dvb: Extend dvb_channel struct, needs to know whether channel is S2.

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.

stream/dvbin.h

@@ -63,6 +63,7 @@ typedef struct {
         int                             freq, srate, diseqc, tone;
         char                            pol;
         int                             tpid, dpid1, dpid2, progid, ca, pids[DMX_FILTER_SIZE], pids_cnt;
+        bool                            is_dvb_s2;
         fe_spectral_inversion_t         inv;
         fe_modulation_t                 mod;
         fe_transmit_mode_t              trans;