Fix -Os feof_unlocked linknamespace, localplt issues (bug 15105, bug 19463).

Fix -Os feof_unlocked linknamespace, localplt issues (bug 15105, bug 19463).

Continuing the fixes for linknamespace and localplt test failures with
-Os that arise from functions not being inlined in that case, this
patch fixes such failures for feof_unlocked.

The usual approach is followed of adding __feof_unlocked (inlined when
feof_unlocked is), making calls use it when required for namespace
reasons, and using libc_hidden_proto / libc_hidden_weak for the
feof_unlocked weak alias when only localplt but not namespace issues
are involved.  In the case of getaddrinfo.c, use of __feof_unlocked
needs to be conditional since that code is also used in nscd (where
__feof_unlocked is not available).

Tested for x86_64 (both without -Os to make sure that case continues
to work, and with -Os to make sure all the relevant linknamespace and
localplt test failures are resolved).  Because of other such failures
that remain after this patch, neither of the bugs can yet be closed.

	[BZ #15105]
	[BZ #19463]
	* libio/feof_u.c (feof_unlocked): Rename to __feof_unlocked and
	define as weak alias of __feof_unlocked.  Use libc_hidden_weak.
	* include/stdio.h (feof_unlocked): Use libc_hidden_proto.
	(__feof_unlocked): New declaration, and inline function if
	[__USE_EXTERN_INLINES].
	* iconv/gconv_conf.c (read_conf_file): Call __feof_unlocked
	instead of feof_unlocked.
	* intl/localealias.c [_LIBC] (FEOF): Likewise.
	* nss/nsswitch.c (nss_parse_file): Likewise.
	* sysdeps/unix/sysv/linux/readonly-area.c (__readonly_area):
	Likewise.
	* time/getdate.c (__getdate_r): Likewise.
	* sysdeps/posix/getaddrinfo.c [IS_IN (libc)] (feof_unlocked):
	Define as macro to call __feof_unlocked.