Adding placeholder for low bandwidth audio test

webrtc/audio/test/low_bandwidth_audio_test.cc

+/*
+ *  Copyright 2017 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.
+ */
+
+// This is a placeholder for the work oprypin@ is doing on a low-bandwidth
+// audio test executable.
+
+int main() {
+  return 0;
+}