include/msvcrt: Replace va_list by __ms_va_list for x86_64.
diff --git a/include/msvcrt/crtdefs.h b/include/msvcrt/crtdefs.h
index fce448e..9eac870 100644
--- a/include/msvcrt/crtdefs.h
+++ b/include/msvcrt/crtdefs.h
@@ -68,6 +68,18 @@
 # endif
 #endif /* __cdecl */
 
+#ifndef __ms_va_list
+# if defined(__x86_64__) && defined (__GNUC__)
+#  define __ms_va_list __builtin_ms_va_list
+#  define __ms_va_start(list,arg) __builtin_ms_va_start(list,arg)
+#  define __ms_va_end(list) __builtin_ms_va_end(list)
+# else
+#  define __ms_va_list va_list
+#  define __ms_va_start(list,arg) va_start(list,arg)
+#  define __ms_va_end(list) va_end(list)
+# endif
+#endif
+
 #ifndef _INTPTR_T_DEFINED
 #ifdef  _WIN64
 typedef __int64 intptr_t;