[FFmpeg-soc] SVQ3 depacketizer

Hi guys, Here is the depacketizer for SVQ3 that Ronald wrote some time ago. To test, you'll need to disable audio until we get QDM2 merged -- thanks Martin for the tip. (s1->skip_media = 1; return; in line 272 of rtsp.c, and add "-an" to your ffmpeg/ffplay parameters). I also updated the Changelog entry with a reference to RTSP-HTTP. Josh