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/system_wrappers/source/thread.cc

@@ -0,0 +1,33 @@
+/*
+ *  Copyright (c) 2011 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/system_wrappers/interface/thread_wrapper.h"
+
+#if defined(_WIN32)
+#include "webrtc/system_wrappers/source/thread_win.h"
+#else
+#include "webrtc/system_wrappers/source/thread_posix.h"
+#endif
+
+namespace webrtc {
+
+#if defined(_WIN32)
+typedef ThreadWindows ThreadType;
+#else
+typedef ThreadPosix ThreadType;
+#endif
+
+rtc::scoped_ptr<ThreadWrapper> ThreadWrapper::CreateThread(
+    ThreadRunFunction func, void* obj, const char* thread_name) {
+  return rtc::scoped_ptr<ThreadWrapper>(
+      new ThreadType(func, obj, thread_name)).Pass();
+}
+
+}  // namespace webrtc