Update audio_processing module

Corresponds to upstream commit 524e9b043e7e86fd72353b987c9d5f6a1ebf83e1

Update notes:

 * Pull in third party license file

 * Replace .gypi files with BUILD.gn to keep track of what changes
   upstream

 * Bunch of new filse pulled in as dependencies

 * Won't build yet due to changes needed on top of these

webrtc/base/platform_file.cc

@@ -0,0 +1,49 @@
+/*
+ *  Copyright 2014 The WebRTC 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.
+ */
+
+#include "webrtc/base/platform_file.h"
+
+#if defined(WEBRTC_WIN)
+#include <io.h>
+#else
+#include <unistd.h>
+#endif
+
+namespace rtc {
+
+#if defined(WEBRTC_WIN)
+const PlatformFile kInvalidPlatformFileValue = INVALID_HANDLE_VALUE;
+
+FILE* FdopenPlatformFileForWriting(PlatformFile file) {
+  if (file == kInvalidPlatformFileValue)
+    return NULL;
+  int fd = _open_osfhandle(reinterpret_cast<intptr_t>(file), 0);
+  if (fd < 0)
+    return NULL;
+
+  return _fdopen(fd, "w");
+}
+
+bool ClosePlatformFile(PlatformFile file) {
+  return CloseHandle(file) != 0;
+}
+#else
+const PlatformFile kInvalidPlatformFileValue = -1;
+
+FILE* FdopenPlatformFileForWriting(PlatformFile file) {
+  return fdopen(file, "w");
+}
+
+bool ClosePlatformFile(PlatformFile file) {
+  return close(file);
+}
+#endif
+
+}  // namespace rtc