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.

/*
 * This header file holds miscellaneous internal definitions for themwi-mgw.
 */

#define	RTP_PACKET_SIZE_GSM_FR	45
#define	RTP_PACKET_SIZE_GSM_EFR	43
#define	RTP_PACKET_SIZE_BFI	14

#define	SAMPLES_PER_FRAME	160