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/rw_lock_posix.cc

@@ -0,0 +1,51 @@
+/*
+ *  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/source/rw_lock_posix.h"
+
+namespace webrtc {
+
+RWLockPosix::RWLockPosix() : lock_() {
+}
+
+RWLockPosix::~RWLockPosix() {
+  pthread_rwlock_destroy(&lock_);
+}
+
+RWLockPosix* RWLockPosix::Create() {
+  RWLockPosix* ret_val = new RWLockPosix();
+  if (!ret_val->Init()) {
+    delete ret_val;
+    return NULL;
+  }
+  return ret_val;
+}
+
+bool RWLockPosix::Init() {
+  return pthread_rwlock_init(&lock_, 0) == 0;
+}
+
+void RWLockPosix::AcquireLockExclusive() {
+  pthread_rwlock_wrlock(&lock_);
+}
+
+void RWLockPosix::ReleaseLockExclusive() {
+  pthread_rwlock_unlock(&lock_);
+}
+
+void RWLockPosix::AcquireLockShared() {
+  pthread_rwlock_rdlock(&lock_);
+}
+
+void RWLockPosix::ReleaseLockShared() {
+  pthread_rwlock_unlock(&lock_);
+}
+
+}  // namespace webrtc