[rtp_rtcp] rtcp::Empty moved into own file and renamed to CompoundPacket on the way

webrtc/modules/rtp_rtcp/source/rtcp_packet/compound_packet.cc

+/*
+ *  Copyright (c) 2016 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/modules/rtp_rtcp/source/rtcp_packet/compound_packet.h"
+
+namespace webrtc {
+namespace rtcp {
+
+bool CompoundPacket::Create(uint8_t* packet,
+                            size_t* index,
+                            size_t max_length,
+                            RtcpPacket::PacketReadyCallback* callback) const {
+  return true;
+}
+
+size_t CompoundPacket::BlockLength() const {
+  return 0;
+}
+
+}  // namespace rtcp
+}  // namespace webrtc