Change RtpRtcp::SetRemb signature to match RtcpTransceiver::SetRemb

in particular change bitrate type to int64_t to follow style guide.

With an extra interface it will allow to add both RtpRtcp module
and RtcpTransceiver as feedback sender to PacketRouter

Bug: webrtc:8239
Change-Id: I9ea265686d7cd2d709f0b42e8a983ebe1790a6ba
Reviewed-on: https://webrtc-review.googlesource.com/32302
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21250}

modules/rtp_rtcp/source/rtcp_transceiver.h

@@ -40,7 +40,7 @@ class RtcpTransceiver {
 
   // (REMB) Receiver Estimated Max Bitrate.
   // Includes REMB in following compound packets.
-  void SetRemb(int bitrate_bps, std::vector<uint32_t> ssrcs);
+  void SetRemb(int64_t bitrate_bps, std::vector<uint32_t> ssrcs);
   // Stops sending REMB in following compound packets.
   void UnsetRemb();