Adds support for VP8 partitions

This change adds support for VP8 partitions in the video jitter buffer and 
the VP8 encoder and decoder wrappers. The feature is currently disabled by
default since it requires a later version of libvpx.

With this change the jitter buffer will also start keeping track of each
packet header until decoding, and the VCMSessionInfo and VCMPacket objects 
will keep pointers into the encoded frame buffers.
Review URL: http://webrtc-codereview.appspot.com/137021

git-svn-id: http://webrtc.googlecode.com/svn/trunk@558 4adac7df-926f-26a2-2b94-8c16560cd09d

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

@@ -21,6 +21,7 @@ namespace webrtc
 class VCMPacket
 {
 public:
+    VCMPacket();
     VCMPacket(const WebRtc_UWord8* ptr,
                    const WebRtc_UWord32 size,
                    const WebRtcRTPHeader& rtpHeader);
@@ -30,6 +31,8 @@ public:
                    WebRtc_UWord32 timestamp,
                    bool markerBit);
 
+    void Reset();
+
     WebRtc_UWord8           payloadType;
     WebRtc_UWord32          timestamp;
     WebRtc_UWord16          seqNum;
@@ -48,7 +51,7 @@ public:
                                         // first
                                         // byte should be ORed with the last packet of the
                                         // previous frame.
-    const RTPVideoHeader *codecSpecificHeader;
+    RTPVideoHeader codecSpecificHeader;
 
 protected:
     void CopyCodecSpecifics(const RTPVideoHeader& videoHeader);