brk.2, chdir.2, chmod.2, chown.2, chroot.2, getpagesize.2, getsid.2, killpg.2, mknod...

brk.2, chdir.2, chmod.2, chown.2, chroot.2, getpagesize.2, getsid.2, killpg.2, mknod.2, readlink.2, setpgid.2, setreuid.2, sigaltstack.2, stat.2, symlink.2, sync.2, truncate.2, vfork.2, wait.2, wait4.2, a64l.3, acosh.3, asinh.3, atanh.3, cbrt.3, ecvt.3, expm1.3, gcvt.3, getcwd.3, getdate.3, getdtablesize.3, getgrent.3, gethostid.3, getpass.3, getpwent.3, getsubopt.3, ilogb.3, insque.3, lockf.3, log1p.3, logb.3, mkstemp.3, mktemp.3, nextafter.3, posix_memalign.3, random.3, realpath.3, remainder.3, rint.3, scalb.3, siginterrupt.3, sigset.3, strdup.3, ualarm.3, usleep.3: Remove references to _XOPEN_SOURCE_EXTENDED in SYNOPSIS

_XOPEN_SOURCE_EXTENDED is obsolete (it existed in SUSv1, but not
subsequent standards). _XOPEN_SOURCE >= 500 produces the same
effects as (_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED). Modifying
the SYNOPSIS of various ages that contain:

    _XOPEN_SOURCE\ >=\ 500 ||
        _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED

to just:

    _XOPEN_SOURCE\ >=\ 500

This has the following benefits:

a) Simplifying the SYNOPSIS by removing ancient
   historical information.

b) Preventing users from being misled into using
   _XOPEN_SOURCE_EXTENDED in new source code.

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