crt/stdio: Restore `__ms_vw*scanf` wrappers

I thought I moved them somewhere in e46c5521375dd28, but I didn't. Sorry.

As these are not MSVCRT functions I decide not to keep them together with
others above.

Signed-off-by: Liu Hao <lh_mouse@126.com>
diff --git a/mingw-w64-headers/crt/stdio.h b/mingw-w64-headers/crt/stdio.h
index 47afb35..d7beb27 100644
--- a/mingw-w64-headers/crt/stdio.h
+++ b/mingw-w64-headers/crt/stdio.h
@@ -1263,6 +1263,9 @@
   int __cdecl swscanf(const wchar_t * __restrict__ _Src,const wchar_t * __restrict__ _Format,...) __MINGW_ATTRIB_DEPRECATED_SEC_WARN;
   int __cdecl wscanf(const wchar_t * __restrict__ _Format,...) __MINGW_ATTRIB_DEPRECATED_SEC_WARN;
 #ifndef __NO_ISOCEXT  /* externs in libmingwex.a */
+  int __cdecl __ms_vwscanf (const wchar_t * __restrict__ , va_list);
+  int __cdecl __ms_vfwscanf (FILE * __restrict__ ,const wchar_t * __restrict__ ,va_list);
+  int __cdecl __ms_vswscanf (const wchar_t * __restrict__ ,const wchar_t * __restrict__ ,va_list);
 
   __mingw_ovr
   __MINGW_ATTRIB_NONNULL(2)