Propagate codec specific info to decoder

Add explicit use of CodecSpecificInfo to VCMGenericDecoder and
the codecs (VP8 and I420). Propagate information from
WebRtcRTPHeader in VCM (IncomingPacket) to GenericDecoder.
Review URL: http://webrtc-codereview.appspot.com/109011

git-svn-id: http://webrtc.googlecode.com/svn/trunk@390 4adac7df-926f-26a2-2b94-8c16560cd09d

src/modules/video_coding/main/source/packet.h

@@ -48,6 +48,7 @@ public:
                                         // first
                                         // byte should be ORed with the last packet of the
                                         // previous frame.
+    const RTPVideoHeader *codecSpecificHeader;
 
 protected:
     void CopyCodecSpecifics(const RTPVideoHeader& videoHeader);