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/codecs/interface/video_codec_interface.h

@@ -201,6 +201,11 @@ public:
     //          - inputImage        : Encoded image to be decoded
     //          - missingFrames     : True if one or more frames have been lost
     //                                since the previous decode call.
+    //          - fragmentation     : Specifies where the encoded frame can be
+    //                                split into separate fragments. The meaning
+    //                                of fragment is codec specific, but often
+    //                                means that each fragment is decodable by
+    //                                itself.
     //          - codecSpecificInfo : Pointer to codec specific data
     //          - renderTimeMs      : System time to render in milliseconds. Only
     //                                used by decoders with internal rendering.
@@ -209,6 +214,7 @@ public:
     virtual WebRtc_Word32
     Decode(const EncodedImage& inputImage,
            bool missingFrames,
+           const RTPFragmentationHeader* fragmentation,
            const CodecSpecificInfo* codecSpecificInfo = NULL,
            WebRtc_Word64 renderTimeMs = -1) = 0;