stream_dvb: restore --dvbin-file option

Got lost some time ago. Although I'm not sure if it actually does
anything on MPlayer (it exists there, but might broken, not sure).

Fixes #988 (untested).

stream/dvbin.h

@@ -95,6 +95,7 @@ typedef struct dvb_params {
         char *cfg_prog;
         int cfg_card;
         int cfg_timeout;
+        char *cfg_file;
 } dvb_priv_t;