libvpx: Pull from upstream

source/libvpx/vpx_ports/msvc.h

 /*
  *  Copyright (c) 2015 The WebM project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
+
+#ifndef VPX_PORTS_MSVC_H_
+#define VPX_PORTS_MSVC_H_
+#ifdef _MSC_VER
+
 #include "./vpx_config.h"
-#define RTCD_C
-#include "./vpx_dsp_rtcd.h"
-#include "vpx_ports/vpx_once.h"
 
-void vpx_dsp_rtcd() {
-  once(setup_rtcd_internal);
-}
+# if _MSC_VER < 1900  // VS2015 provides snprintf
+#  define snprintf _snprintf
+# endif  // _MSC_VER < 1900
+
+#endif  // _MSC_VER
+#endif  // VPX_PORTS_MSVC_H_