If VDR-channel-config is used, we know the service_id.
Using that, PMT can be extracted from PAT (code for that
inspired by szap-s2 again).
For this, we need to demux PAT with a special filter-setup,
and once PMT was found it can be added to the PID-list.
PMT is only resolved the first time one tunes to a channel,
then stored in the channel-list in memory.
With PMT available, ffmpeg can safely decode the teletext-pids.
Now also "stream ID" (for DVB-S2) and "inversion" are understood.
The parameter-string can also provide information on FEC, rolloff etc. For DVB-S, "auto" which mpv uses by default should be fine, I can also confirm it works. For non-DVB-S cards, it might be useful to also parse this information in case of a vdr-channel list.
As I have no such hardware and thus would have to do it blindly, I added a FIXME.
Mostly complete vdr-channels.conf format documentation is at http://www.vdr-wiki.de/wiki/index.php/Channels.conf (german only).
It contains now also a boolean which tells whether this is an DVB-S2 channel (not initialized yet - tbd in next commit).
We could also pass through the type of the delivery system (would be more flexible), but the delivery-system-enum is only available with S2API, so this is more backwards-compatible.
If someone has DVB-T2 / DVB-C2 hardware and extends the code to deal with it, this should be changed.
