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

Building with -Os produces linknamespace and localplt failures for,
among other functions, gnu_dev_major, gnu_dev_minor and
gnu_dev_makedev.

The issue is that those functions are not inlined when building with
-Os.  While one could force them to be inlined in that case, it seems
more natural to fix this issue similarly to other namespace issues.
Thus, this patch makes gnu_dev_* into weak aliases for hidden symbols
__gnu_dev_*; __gnu_dev_* are then defined as inlines in the internal
include/sys/sysmacros.h, and uses of gnu_dev_* (often via the macros
major, minor and makedev) for which there are namespace issues are
changed to use __gnu_dev_*; where there are no namespace issues, use
of libc_hidden_proto serves to avoid unnecessary local PLT entry use.

Tested for x86_64, (a) without -Os, to verify the testsuite continues
to pass without problems and that the functions called under their new
names continue to be inlined as expected in that case; (b) with -Os,
to verify that the linknamespace and localplt failures in question go
away (but because of other such failures present, neither of the
relevant bugs can yet be closed).

	[BZ #15105]
	[BZ #19463]
	* include/sys/sysmacros.h [!_ISOMAC]
	(__SYSMACROS_NEED_IMPLEMENTATION): Define macro.
	[!_SYS_SYSMACROS_H_WRAPPER && !_ISOMAC]
	(_SYS_SYSMACROS_H_WRAPPER): Likewise.
	[!_SYS_SYSMACROS_H_WRAPPER && !_ISOMAC] (gnu_dev_major): Use
	libc_hidden_proto.
	[!_SYS_SYSMACROS_H_WRAPPER && !_ISOMAC] (gnu_dev_minor): Likewise.
	[!_SYS_SYSMACROS_H_WRAPPER && !_ISOMAC] (gnu_dev_makedev):
	Likewise.
	[!_SYS_SYSMACROS_H_WRAPPER && !_ISOMAC] (__SYSMACROS_DECL_TEMPL):
	Undefine and redefine to add use __gnu_dev_ prefix.
	[!_SYS_SYSMACROS_H_WRAPPER && !_ISOMAC] (__SYSMACROS_IMPL_TEMPL):
	Likewise.
	[!_SYS_SYSMACROS_H_WRAPPER && !_ISOMAC] (__gnu_dev_major): Declare
	and define as hidden inline function.
	[!_SYS_SYSMACROS_H_WRAPPER && !_ISOMAC] (__gnu_dev_minor):
	Likewise.
	[!_SYS_SYSMACROS_H_WRAPPER && !_ISOMAC] (__gnu_dev_makedev):
	Likewise.
	* misc/makedev.c (OUT_OF_LINE_IMPL_TEMPL): Use __gnu_dev_ prefix.
	(gnu_dev_major): Use weak_alias and libc_hidden_weak.
	(gnu_dev_minor): Likewise.
	(gnu_dev_makedev): Likewise.
	* csu/check_fds.c (check_one_fd): Use __gnu_dev_makedev instead of
	makedev.
	* posix/wordexp.c (exec_comm_child): Likewise.
	* sysdeps/mach/hurd/xmknodat.c (__xmknodat): Use __gnu_dev_minor
	instead of minor and __gnu_dev_major instead of major.
	* sysdeps/unix/sysv/linux/device-nrs.h (DEV_TTY_P): Use
	__gnu_dev_major instead of major.
	* sysdeps/unix/sysv/linux/pathconf.c (distinguish_extX): Use
	__gnu_dev_major instead of gnu_dev_major and __gnu_dev_minor
	instead of gnu_dev_minor.
	* sysdeps/unix/sysv/linux/ptsname.c (MASTER_P): Likewise.
	(SLAVE_P): Likewise.
	(__ptsname_internal): Use __gnu_dev_minor instead of minor.
	* sysdeps/unix/sysv/linux/ttyname.h (is_pty): Use __gnu_dev_major
	instead of major.

sysdeps/unix/sysv/linux/pathconf.c

@@ -73,7 +73,7 @@ distinguish_extX (const struct statfs *fsbuf, const char *file, int fd)
     return EXT2_LINK_MAX;
 
   __snprintf (buf, sizeof (buf), "/sys/dev/block/%u:%u",
-	      gnu_dev_major (st.st_dev), gnu_dev_minor (st.st_dev));
+	      __gnu_dev_major (st.st_dev), __gnu_dev_minor (st.st_dev));
 
   ssize_t n = __readlink (buf, path, sizeof (path));
   if (n != -1 && n < sizeof (path))