* wincap.h (wincaps::has_always_all_codepages): New element.

	* wincap.h (wincaps::has_always_all_codepages): New element.
	* wincap.cc: Implement above element throughout.
	* wchar.h (__sjis_mbtowc): Declare.
	(__eucjp_mbtowc): Ditto.
	(__gbk_mbtowc): Ditto.
	(__kr_mbtowc): Ditto.
	(__big5_mbtowc): Ditto.
	* syscalls.cc (internal_setlocale): Convert to char * function.
	Return parameter by default.  Return NULL if request to use a
	charset can't be satisfied due to missing codepage support in the
	underlying OS.  Fix comment.
	(setlocale): Store original locale.  Restore to original locale if
	internal_setlocale returns NULL.