Make uselocale support static linking.

Make uselocale support static linking.

	* locale/xlocale.c: Revert changes putting _nl_global_locale here.
	This file again just defines _nl_C_locobj.
	(_nl_C_locobj): Use a categories.def iterator in the initializer.
	* locale/global-locale.c: New file.  Define _nl_global_locale here,
	using all weak references in the initializer.
	* locale/Makefile (aux): Add global-locale.
	* locale/localeinfo.h (_nl_global_locale, _NL_CURRENT_LOCALE): Make
	these unconditional, along with the tsd decl.
	[!SHARED && HAVE___THREAD && HAVE_WEAK_SYMBOLS] (NL_CURRENT_INDIRECT):
	Define it under these conditions.
	[NL_CURRENT_INDIRECT]: Test this instead of [! SHARED].
	Don't declare _nl_current.  Declare _nl_current_LC_FOO as
	`extern __thread struct locale_data *const *'.
	[NL_CURRENT_INDIRECT]
	(_NL_CURRENT_DATA, _NL_CURRENT, _NL_CURRENT_WSTR): Add indirection.
	[NL_CURRENT_INDIRECT] (_NL_CURRENT_DEFINE): Rewritten.  Define
	the thread variable _nl_current_LC_FOO and also a special absolute
	symbol _nl_current_LC_FOO_used.
	* locale/uselocale.c (__uselocale) [NL_CURRENT_INDIRECT]:
	Set each _nl_current_LC_FOO symbol to point into the new locale,
	using weak references to test if _nl_current_LC_FOO_used was linked in.
	* locale/setlocale.c [! SHARED]: Replace this conditional ...
	[NL_CURRENT_INDIRECT]: ... with this one.
	(_nl_current, _nl_C): Variables removed.
	[NL_CURRENT_INDIRECT] (_nl_current_used): New variable, table of
	weak references to _nl_current_LC_FOO_used.
	[NL_CURRENT_INDIRECT] (CATEGORY_USED): Define using that table.
	(free_category): New function, broken out of ...
	(free_mem): ... here.  Call that.
	(free_mem) [NL_CURRENT_INDIRECT]: Use a categories.def iterator
	instead of a loop.

	__USING_NAMESPACE_C99 depending on _GLIBCPP_USE_NAMESPACES.