Fix regcomp wcscoll, wcscmp namespace (bug 18497).

regcomp brings in references to wcscoll, which isn't in all the
standards that contain regcomp.  In turn, wcscoll brings in references
to wcscmp, also not in all those standards.  This patch fixes this by
making those functions into weak aliases of __wcscoll and __wcscmp and
calling those names instead as needed.

Tested for x86_64 and x86 (testsuite, and that disassembly of
installed shared libraries is unchanged by the patch).

	[BZ #18497]
	* wcsmbs/wcscmp.c [!WCSCMP] (WCSCMP): Define as __wcscmp instead
	of wcscmp.
	(wcscmp): Define as weak alias of WCSCMP.
	* wcsmbs/wcscoll.c (STRCOLL): Define as __wcscoll instead of
	wcscoll.
	(USE_HIDDEN_DEF): Define.
	[!USE_IN_EXTENDED_LOCALE_MODEL] (wcscoll): Define as weak alias of
	__wcscoll.  Don't use libc_hidden_weak.
	* wcsmbs/wcscoll_l.c (STRCMP): Define as __wcscmp instead of
	wcscmp.
	* sysdeps/i386/i686/multiarch/wcscmp-c.c
	[SHARED] (libc_hidden_def): Define __GI___wcscmp instead of
	__GI_wcscmp.
	(weak_alias): Undefine and redefine.
	* sysdeps/i386/i686/multiarch/wcscmp.S (wcscmp): Rename to
	__wcscmp and define as weak alias of __wcscmp.
	* sysdeps/x86_64/wcscmp.S (wcscmp): Likewise.
	* include/wchar.h (__wcscmp): Declare.  Use libc_hidden_proto.
	(__wcscoll): Likewise.
	(wcscmp): Don't use libc_hidden_proto.
	(wcscoll): Likewise.
	* posix/regcomp.c (build_range_exp): Call __wcscoll instead of
	wcscoll.
	* posix/regexec.c (check_node_accept_bytes): Likewise.
	* conform/Makefile (test-xfail-XPG3/regex.h/linknamespace): Remove
	variable.
	(test-xfail-XPG4/regex.h/linknamespace): Likewise.
	(test-xfail-POSIX/regex.h/linknamespace): Likewise.