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"
 
 # if _MSC_VER < 1900  // VS2015 provides snprintf
 #  define snprintf _snprintf
 # endif  // _MSC_VER < 1900
 
+#if _MSC_VER < 1800  // VS2013 provides round
+#include <math.h>
+static INLINE double round(double x) {
+  if (x < 0)
+    return ceil(x - 0.5);
+  else
+    return floor(x + 0.5);
+}
+#endif  // _MSC_VER < 1800
+
 #endif  // _MSC_VER
 #endif  // VPX_PORTS_MSVC_H_