Various pages: Remove explicit blank lines, replacing them with .PP when appropriate

Rationale:
$ man 7 man-pages 2>/dev/null | sed -n /Paragraphs/,/^$/p
       Paragraphs should be separated by suitable markers (usually
       either .PP or .IP).  Do not separate paragraphs using blank
       lines,  as  this  results  in poor rendering in some output
       formats (such as PostScript and PDF).

Fix:
$ sed -i -e '1,/^\.EX/s/^$/.PP/' -e '/^\.EE/,/^\.EX/s/^$/.PP/' man?/*

And then some manual adjustments.

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

syscall.2: Update superh syscall convention

I noticed this while working on some silly "hello, world"
programs, see https://git.sr.ht/~phf/hello-again if you're
curious.  Disassembling sh4 code showed trap #31 all over the
place but the syscall(2) man page talked about trap #0x17 and
friends. Checking the kernel sources I got lucky in
arch/sh/kernel/entry-common.S where in commit 3623d138213ae Rich
Felker clarifies the situation.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

mallinfo2.3: New link to mallinfo(3)

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

mallinfo.3: Update example program to use mallinfo2()

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

mallinfo.3: Document mallinfo2() and note that mallinfo() is deprecated

Document the mallinfo2() function added in glibc 2.33.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

ld.so.8: srcfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

ld.so.8: Document the --argv0 option added in glibc 2.33

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

ftime.3: glibc 2.33 has removed ftime()

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

getrusage.2: Starting in 2.33, glibc no longer provides vtimes()

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

pthread_attr_setsigmask_np.3: tfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

nl_langinfo.3: tfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

isfdtype.3: tfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

aio_suspend.3: tfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

setns.2: tfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

perf_event_open.2: wfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

statfs.2: tfix (Section number)

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

Changes.old: Minor fixes to 5.10 changelog

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

Start of man-pages-5.11: updating Changes and Changes.old

Start of man-pages-5.11: updating .Announce and .lsm files

Start of man-pages-5.11: renaming .Announce and .lsm files

Ready for 5.10

getent.1, access.2, cacheflush.2, chroot.2, clock_getres.2, fcntl.2, getrusage.2, io_cancel.2, io_destroy.2, io_getevents.2, io_setup.2, io_submit.2, link.2, llseek.2, mmap.2, mount.2, readv.2, restart_syscall.2, semctl.2, set_mempolicy.2, set_tid_address.2, shmctl.2, sigaction.2, sigaltstack.2, spu_create.2, statfs.2, subpage_prot.2, syscalls.2, timer_getoverrun.2, uselib.2, INFINITY.3, __ppc_set_ppr_med.3, bstring.3, btree.3, ctime.3, fgetc.3, fopen.3, getcontext.3, gethostbyname.3, getnetent.3, getprotoent.3, getservent.3, inet.3, j0.3, list.3, makecontext.3, nextafter.3, posix_memalign.3, profil.3, pthread_tryjoin_np.3, puts.3, rcmd.3, resolver.3, rtime.3, sigsetops.3, strnlen.3, tailq.3, elf.5, filesystems.5, nscd.conf.5, proc.5, utmp.5, attributes.7, ipv6.7, packet.7, pthreads.7, signal-safety.7, signal.7, spufs.7, system_data_types.7, tcp.7: tstamp

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

Changes: Ready for 5.10

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

rcmd.3: SEE ALSO: remove intro(2)

There's no reason to link to intro(2)...

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

cacheflush.2: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

cacheflush.2: Document Architecture-specific variants

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

cacheflush.2: Document __builtin___clear_cache() as a more portable alternative

Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Cc: Martin Sebor <msebor@redhat.com>
Cc: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

packet.7: Update references to kernel documentation

Files moved from .txt to .rst.

Also, drop / prefix from kernel source tree references.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

filesystems.5: wfix: ntfs: remove FAT comparison

The main point I was driving at with this patch was to fix
"Microsoft Window's FAT filesystems" (i.e., FAT filesystems which
belong to Microsoft Windows, which is decidedly wrong).

FAT32 first shipped with MS-DOS 7.1, as part of Windows 95 OSR2,
but it's a (relatively) simple logical extension of the previous
FATx filesystems (16 and 12 as we know and love them today, I
don't think the PC ever saw 8), hence the "VFAT" driver name ‒
calling FAT-anything a Windows filesystem would be a flat-out lie,
calling it a Microsoft filesystem would be, uh, facetious.

NTFS (as part of Windows NT), on the other hand, is wholly
different WRT the scope and feature-set (it does borrow some
layouting from FAT, but reading NTFS as FAT doesn't get you very
far, or much).

The replacing bit is also questionable, especially in a.d. 2020:
while it is true that you cannot install NT on FAT (after a
certain point? my memory ain't what it used to be), and must
therefore replace your existing FAT partitions with NTFS during
upgrades; Windows NT 4.0, the last product to be NT-branded came
out in 1996, i.e. you could not install Windows on FAT (and,
therefore, upgrade it to NTFS, replacing it) during my entire
lifetime.

Indeed, in $(date +%Y) we live in a post-NTFS world ‒ putting NTFS
in the same class as FAT beyond "is a filesystem" is a joke.

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

filesystems.5: Note ncpfs removal from kernel

Relevant Linux commits:
 * moved to staging in 1bb8155080c652c4853e6228f8f0d262b3049699
   (describe: v4.15-rc1-129-g1bb8155080c6) in Nov 2017,
   described as "broken" and "obsolete"
 * purged in bd32895c750bcd2b511bf93917bf7ae723e3d0b6
   (describe: v4.17-rc3-1010-gbd32895c750b) in Jun 2018,
   "since no one has complained or even noticed it was gone"

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

filesystems.5: Fix link to user space tooling for ncpfs

Corresponds to Linux commit 1b83df308f69a5a3cc59be03bd7fb23e4bcebd8e

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

pthreads.7: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

pthreads.7: Rephrase function list in terms of POSIX rather than SUS

The list was using an inconsistent mixture of "POSIX" and "SUS".

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

regex.3: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

pthread_attr_setguardsize.3: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

pthread_attr_setstacksize.3: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

pthread_mutexattr_setrobust.3: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

pthread_attr_setstackaddr.3: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

pthread_attr_setdetachstate.3: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

setns.2: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

elf.5: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

perf_event_open.2: tfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

mount_namespaces.7: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

strtol.3: tfix

Signed-off-by: John A. Leuenhagen <john@zlima12.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

elf.5: srcfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

elf.5: SEE ALSO: add objcopy(1)

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

tcp.7: tcp_syncookies: It is now an integer [0, 2]

Since Linux kernel 3.12, tcp_syncookies can have the value 2,
which sends out cookies unconditionally.

Related kernel commits:
5ad37d5deee1ff7150a2d0602370101de158ad86
d8513df2598e5142f8a5c4724f28411936e1dfc7

Reported-by: Philip Rowlands <linux-kernel@dimebar.com>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

modf.3: tfix

See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=976312

Reported-by: Bill Allombert <ballombe@debian.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

keyctl.2: tfix

Fixes: fa76da808eff
Signed-off-by: Arusekk <arek_koz@o2.pl>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

strnlen.3: Fix a small inconsistency in the text

Quoting Heinrich:

    The strnlen.3 manpage has the following sentence:

    "In doing this, strnlen() looks only at the first maxlen
    characters in the string pointed to by s and never beyond
    s+maxlen."

    This sentence is self-contradictory:

    The last visited character implied by "first maxlen
    characters" is s[maxlen-1].

    Given that "beyond a" does not include "a", the last visited
    character implied by "never beyond s+maxlen" is s[maxlen].

    A consistent sentence would be

    "In doing this, strnlen() looks only at the first maxlen
    characters in the string pointed to by s and never beyond
    s+maxlen-1."

    I would prefer

    "In doing this, strnlen() looks only at the first maxlen
    characters in the string pointed to by s and never beyond
    s[maxlen-1]"

Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

subpage_prot.2: SYNOPSIS: Fix return type: s/long/int/

The Linux kernel uses 'int' instead of 'long' for the return type.
As glibc provides no wrapper, use the same type the kernel uses.

......

$ grep -n wrapper man-pages/man2/subpage_prot.2
40:There is no glibc wrapper for this system call; see NOTES.
99:Glibc does not provide a wrapper for this system call; call it using

$ grep -rn SYSCALL_DEFINE.*subpage_prot linux/;
linux/arch/powerpc/mm/book3s64/subpage_prot.c:190:
SYSCALL_DEFINE3(subpage_prot, unsigned long, addr,

$ sed -n /SYSCALL.*subpage_prot/,/^}/p \
  linux/arch/powerpc/mm/book3s64/subpage_prot.c \
  |grep return;
return -ENOENT;
return -EINVAL;
return -EINVAL;
return 0;
return -EFAULT;
return -EFAULT;
return err;

$ sed -n /SYSCALL.*subpage_prot/,/^}/p \
  linux/arch/powerpc/mm/book3s64/subpage_prot.c \
  |grep '\<err\>';
int err;
err = -ENOMEM;
err = -ENOMEM;
err = 0;
return err;

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

spu_create.2: Clarify that spu_create() now has 4 arguments but once had only 3

Reported-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

spu_create.2: Relocate paragraph on 'mode' argument

This paragraph is a little bit hidden at the end of DESCRIPTION;
make it a little more prominent.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

spu_create.2: Add kernel version numbers for SPU_CREATE_AFFINITY_SPU/_MEM

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

spu_run.2: srcfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

getpriority.2: wfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

getpriority.2: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

link.2: ffix

Reported-by: Alejandro Colomar (man-pages) <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

link.2: ERRORS: add ENOENT when target is deleted

Linux kernel commit aae8a97d3ec30788790d1720b71d76fd8eb44b73 (part
of kernel release v2.6.39) added a check to disallow creating a
hardlink to an unlinked file.

The manual page already describes the trick of using
AT_SYMLINK_FOLLOW as an alternative to AT_EMPTY_PATH, and for
AT_EMPTY_PATH the manual page already notes that it "will
generally not work if the file has a link count of zero". However,
the precise error (ENOENT) is not mentioned, and the error case
isn't mentioned in the ERRORS section at all.

This makes it easy to overlook the fact that the AT_SYMLINK_FOLLOW
trick on /proc/self/fd/NN won't work on deleted files, as
evidenced by the follow message (which turns up when googling
"linkat deleted ENOENT"):
https://groups.google.com/g/linux.kernel/c/zZO4lqqwp64

Signed-off-by: Mathias Rav <m@git.strova.dk>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

fanotify.7: fix outdated description

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

pivot_root.2: tfix

Reported-by: Davide Giorgio <davide@giorgiodavide.it>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

getrusage.2: Note that the 'vtimes' symbol exists only up to glibc 2.32

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

set_tid_address.2: SYNOPSIS: Fix set_tid_address() return type

The Linux kernel uses 'pid_t' instead of 'long' for the return type.
As glibc provides no wrapper, use the same types the kernel uses.

$ sed -n 34,36p man-pages/man2/set_tid_address.2
.PP
.IR Note :
There is no glibc wrapper for this system call; see NOTES.

$ grep -rn 'SYSCALL_DEFINE.*set_tid_address' linux/
linux/kernel/fork.c:1632:
SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)

$ sed -n 1632,1638p linux/kernel/fork.c
SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
{
current->clear_child_tid = tidptr;

return task_pid_vnr(current);
}

$ grep -rn 'task_pid_vnr(struct' linux/
linux/include/linux/sched.h:1374:
static inline pid_t task_pid_vnr(struct task_struct *tsk)

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

restart_syscall.2: SYNOPSIS: Fix restart_syscall() return type

The Linux kernel uses 'long' instead of 'int' for the return type.
As glibc provides no wrapper, use the same types the kernel uses.

$ grep -rn 'SYSCALL_DEFINE.*(restart_syscall'
kernel/signal.c:2891:SYSCALL_DEFINE0(restart_syscall)

$ sed -n 2891,2895p kernel/signal.c
SYSCALL_DEFINE0(restart_syscall)
{
struct restart_block *restart = &current->restart_block;
return restart->fn(restart);
}

$ grep -rn 'struct restart_block {'
include/linux/restart_block.h:25:struct restart_block {

$ sed -n 25,56p include/linux/restart_block.h
struct restart_block {
long (*fn)(struct restart_block *);
union {
/* For futex_wait and futex_wait_requeue_pi */
struct {
u32 __user *uaddr;
u32 val;
u32 flags;
u32 bitset;
u64 time;
u32 __user *uaddr2;
} futex;
/* For nanosleep */
struct {
clockid_t clockid;
enum timespec_type type;
union {
struct __kernel_timespec __user *rmtp;
struct old_timespec32 __user *compat_rmtp;
};
u64 expires;
} nanosleep;
/* For poll */
struct {
struct pollfd __user *ufds;
int nfds;
int has_timeout;
unsigned long tv_sec;
unsigned long tv_nsec;
} poll;
};
};

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

attributes.7: SEE ALSO: add signal-safety(7)

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

lseek64.3: tfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

pthread_tryjoin_np.3: Note that pthread_timedjoin_np() uses CLOCK_REALTIME, but there's a bug

Learned from an email converasation with Mike Crowe, and
verified by experiment.

Reported-by: Mike Crowe <mac@mcrowe.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

standards.7: Add LFS (Large File Summit)

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

lseek64.3: NOTES: describe the origin of lseek64() in LFS

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

lseek64.3: Remove sentence saying lseek64() is an alias for llseek()

As far as I can see, it is instead simply an alias for a
wrapper that calls _llseek(). Saying it's an alias for "llseek()"
seems confusing.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

lseek64.3: Remove section numbers from interface list

We're talking of a mix of wrapper functions and system calls
in this page. lseek() is both a system and a wrapper function,
and this page is mostly describing the wrapper

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

lseek64.3: wfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

lseek64.3: Minor clarifications

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

lseek64.3: srcfix: add some comments to remind myself of some details

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

llseek.2: Point the reader to lseek64(3) for info about llseek(3)

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

llseek.2: Note size of 'loff_t' type

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

lseek64.3: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

getnameinfo.3: tfix

Reported-by: Sebastian Kirmayer <man-pages@kirmayer.eu>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

lseek64.3: srcfix: Add a lore link to some background on these APIs

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

getnameinfo.3: tfix

Reported-by: Sebastian Kirmayer <sebastian@kirmayer.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

llseek.2: Some mild rewriting to ease reading of the info in this page

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

capget.2, execve.2, readv.2, socketpair.2, utime.2, utimensat.2, getloadavg.3, proc.5, mount_namespaces.7, unix.7: ffix

{.IR var [x]} -> {.I var[x]}

There were around 15 entries of the former,
and around 360 of the latter.

Found using:
$ grep -rn '^\.I[ |R].* \[.*\]' |sort

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

utmp.5: Oxford comma

Found using:
$ grep -rn '\\f., [^ ]*\\f. and' man?

I also updated the markup in that paragraph: \f -> .

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

futex.2: tfix

In the comment of the example program, the peer blocks on fwait()
rather than fpost().

Signed-off-by: Jing Peng <pj.hades@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

standards.7: Relocate the discussion on POSIX manual pages

Rather than mention these pages under the discussion of one
version of the standard, move that text to the end of the page,
where it is probably a little more obvious.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

standards.7: Add URL for POSIX.1-2008/SUSv4

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

standards.7: Fix some URLs for locations of the standards

Reported-by: Rob Landley <rob@landley.net>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

clock_getres.2: Plae ERRORS in alphabetical order

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

socket.7: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

socket.7: tfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

arch_prctl.2: wfix: "current thread" ==> "calling thread"

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

perf_event_open.2: tfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

perf_event_open.2: Minor tweaks

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

perf_event_open.2: Update man page with recent kernel changes

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
[alx: ffix + tfix]
Cowritten-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

signal.7: Add pidfd_send_signal() to list of APIs for sending signals

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

signal.7: ffix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

signal.7: Fixes and additions to text on execution of signal handlers

After comments from Dave Martin.

Reported-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

sigaction.2: Add a cross-reference to signal(7) for further info on 'ucontext_t'

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

signal.7: Mention 'ucontext_t' in the discussion of signal handler execution

Linking up the info presented on this page with the discussion
in getcontext(3) helps the reader.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

makecontext.3: Minor rewording

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>