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.

/*
 * Here we define the structure used to capture the result
 * of From header field parsing.
 */

struct grok_from {
	char		*uri;
	unsigned	uri_len;
	char		*user;
	unsigned	user_len;
	char		*cnam;
	unsigned	cnam_len;
	int		cnam_quoted;
};