1. Updated code to set _lastdecodedSeqNum after clean up of old frames (2/3 instances were updated, 1 was ok).
2. Updated _lastDecodedSeqNum based on empty packets that arrive after the frame which they belong to was already decoded (as was with existing code with regard to filler packets).
B. Code clean up.
Review URL: http://webrtc-codereview.appspot.com/78001
git-svn-id: http://webrtc.googlecode.com/svn/trunk@237 4adac7df-926f-26a2-2b94-8c16560cd09d
