stream_dvb: Add possibility to dump a full transponder.

Was already possible before by injecting the magic PID
8192 into channels.conf, the flag makes this much more
useable and we also have it documented.
Useful not only for debugging, but also for incomplete
channels.conf (mplayer format...), multi-channel
recording, or channels which do dynamic PID switchng.

full-transponder is also useful for channels which switch PIDs on-the-fly.
ffmpeg can handle this, but it needs the full stream with all PIDs.

stream/dvbin.h

@@ -115,6 +115,8 @@ typedef struct dvb_params {
         int cfg_card;
         int cfg_timeout;
         char *cfg_file;
+
+        int cfg_full_transponder;
 } dvb_priv_t;