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/encoded_frame.h

@@ -87,6 +87,8 @@ public:
     */
     const CodecSpecificInfo* CodecSpecific() const {return &_codecSpecificInfo;}
 
+    const RTPFragmentationHeader* FragmentationHeader() const;
+
     WebRtc_Word32 Store(VCMFrameStorageCallback& storeCallback) const;
 
     static webrtc::FrameType ConvertFrameType(VideoFrameType frameType);
@@ -110,6 +112,7 @@ protected:
     bool                          _missingFrame;
     CodecSpecificInfo             _codecSpecificInfo;
     webrtc::VideoCodecType        _codec;
+    RTPFragmentationHeader        _fragmentation;
 };
 
 } // namespace webrtc