mgw: accept zero-length RTP payload as BFI Mainline OsmoBTS now has an option (rtp continuous-streaming) that causes it to emit an RTP packet every 20 ms without gaps, sending a BFI marker in the form of zero-length RTP payload when it has nothing else to send. These codec-independent BFI markers don't indicate TAF, but this provision is a good start. Accept this BFI packet format in themwi-mgw.

/* extern declarations for functions in gsm_call.c module */

extern struct gsm_call *find_gsm_callref();
extern struct gsm_call *find_socket_call();
extern struct gsm_call *create_gsm_call();
extern struct gsm_call *create_new_mt_call();
extern uint32_t alloc_mt_callref();