win64: use new headers from mingw

include/stdarg.h

@@ -2,6 +2,7 @@
 #define _STDARG_H
 
 #ifdef __x86_64__
+#ifndef _WIN64
 #include <stdlib.h>
 
 /* GCC compatible definition of va_list. */
@@ -48,16 +49,21 @@ typedef struct __va_list_struct *va_list;
      *(dest) = *(src))
 #define va_end(ap) __builtin_free(ap)
 
-#else
-
+#else /* _WIN64 */
 typedef char *va_list;
+#define va_start(ap,last) ap = ((char *)&(last)) + ((sizeof(last)+7)&~7)
+#define va_arg(ap,type) (ap += (sizeof(type)+7)&~7, *(type *)(ap - ((sizeof(type)+7)&~7)))
+#define va_copy(dest, src) (dest) = (src)
+#define va_end(ap)
+#endif
 
+#else /* __i386__ */
+typedef char *va_list;
 /* only correct for i386 */
 #define va_start(ap,last) ap = ((char *)&(last)) + ((sizeof(last)+3)&~3)
 #define va_arg(ap,type) (ap += (sizeof(type)+3)&~3, *(type *)(ap - ((sizeof(type)+3)&~3)))
 #define va_copy(dest, src) (dest) = (src)
 #define va_end(ap)
-
 #endif
 
 /* fix a buggy dependency on GCC in libio.h */