* mingwex/mbrtowc.c: New file.

* mingwex/wcrtomb.c: New file.
	* mingwex/btowc.c: New file.
	* mingwex/wctob.c: New file.
	* mingwex/mb_wc_common.h: New file.
	* mingwex/Makefile.in (DISTFILES): Add new files.
	(Q8_OBJS): Add new objects.
	* include/wchar.h: Adjust comment about mbrtowc() and related
	funcions. Add __restrict__ to pointer params in prototypes.
	(wmemset. wmemchr, wmemcpy, wmemmove, wcstoll, wcstoull): Remove
	arg names from protototypes.

winsup/mingw/mingwex/mb_wc_common.h

@@ -0,0 +1,18 @@
+#include <locale.h>
+#include <string.h>
+#include <stdlib.h>
+
+static inline
+unsigned int get_cp_from_locale (void)
+{
+  char* cp_string;
+  /*
+    locale :: "lang[_country[.code_page]]" 
+               | ".code_page"
+
+  */
+
+  if ((cp_string = strchr(setlocale(LC_CTYPE, NULL), '.')))
+    return  ((unsigned) atoi (cp_string + 1));
+  return 0;
+}