Add RTCP packet types to packet builder:
REMB, TMMBR, TMMBN and
extended reports: RRTR, DLRR, VoIP metric.

BUG=2450
R=mflodman@webrtc.org, stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/9299005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6537 4adac7df-926f-26a2-2b94-8c16560cd09d