libvpx: Pull from upstream

source/libvpx/vpx_ports/vpx_once.h

 /*
  *  Copyright (c) 2011 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_ONCE_H
+#define VPX_ONCE_H
+
 #include "vpx_config.h"
 
 #if CONFIG_MULTITHREAD && defined(_WIN32)
 #include <windows.h>
 #include <stdlib.h>
 static void once(void (*func)(void))
 {
     static CRITICAL_SECTION *lock;
     static LONG waiters;
     static int done;
@@ skipping 68 matching lines @@
 {
     static int done;
 
     if(!done)
     {
         func();
         done = 1;
     }
 }
 #endif
+
+#endif