VP8 RTP packetizer rewrite

Rewriting the RTP packetizer for VP8 to accommodate more functionality.
This CL does not change the formatting other than that the kStrict
mode now produces equal-sized fragments.
Review URL: http://webrtc-codereview.appspot.com/33006

git-svn-id: http://webrtc.googlecode.com/svn/trunk@80 4adac7df-926f-26a2-2b94-8c16560cd09d
4 files changed