rtsp.c to detect the ID of the packet source also in case of TCP streams.
This allows proper playback of RDT streams with multiple stream types, e.g.
audio + video. Accepted by LucaB in "RDT/Realmedia patches #2" thread on ML.



git-svn-id: file:///var/local/repositories/ffmpeg/trunk@15496 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b