msvc: Move stdarg.h include ahead of __PHYSFS_msvc_vsnprintf declaration.

(transplanted from e0346f4349265b4e483b987a0694740474942bb0)

src/physfs.c

@@ -12,8 +12,6 @@
 #include "physfs_internal.h"
 
 #if defined(_MSC_VER)
-#include <stdarg.h>
-
 /* this code came from https://stackoverflow.com/a/8712996 */
 int __PHYSFS_msvc_vsnprintf(char *outBuf, size_t size, const char *format, va_list ap)
 {

src/physfs_internal.h

@@ -95,6 +95,7 @@ extern const PHYSFS_Archiver __PHYSFS_Archiver_VDF;
 /* a real C99-compliant snprintf() is in Visual Studio 2015,
    but just use this everywhere for binary compatibility. */
 #if defined(_MSC_VER)
+#include <stdarg.h>
 int __PHYSFS_msvc_vsnprintf(char *outBuf, size_t size, const char *format, va_list ap);
 int __PHYSFS_msvc_snprintf(char *outBuf, size_t size, const char *format, ...);
 #define vsnprintf __PHYSFS_msvc_vsnprintf