Implemented a new VP8 packetizer with three modes. The packetizer
class needs access to the fragmentation information, which is
now created in the codec wrapper and passed through the callback
chain to the RTPSenderVideo::SendVP8().
A unit test for the VP8 packetizer was also implemented. It tests the
three different modes. The tests could definitely be more elaborate.
Review URL: http://webrtc-codereview.appspot.com/34003
git-svn-id: http://webrtc.googlecode.com/svn/trunk@48 4adac7df-926f-26a2-2b94-8c16560cd09d
