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 various internal definitions for DTMF generation,
 * including DTMF_MAX_FRAMES limit.
 */

#define	DTMF_MAX_FRAMES		60	/* 1200 ms */

struct dtmf_desc {
	int	digit;
	float	freq_low;
	float	freq_high;
	int16_t	*samples;
};