Propagate capture ntp timestamp from rtp to renderer.

Mostly the interface changes, the real implementation of ntp timestamp will come in a follow up cl.

TEST=new tests and try bots
BUG=3111
R=niklas.enbom@webrtc.org, stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/11469004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5911 4adac7df-926f-26a2-2b94-8c16560cd09d

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

@@ -33,6 +33,8 @@ public:
 
     uint8_t           payloadType;
     uint32_t          timestamp;
+    // NTP time of the capture time in local timebase in milliseconds.
+    int64_t ntp_time_ms_;
     uint16_t          seqNum;
     const uint8_t*    dataPtr;
     uint32_t          sizeBytes;