[core] add SEND_RTCP_MESSAGE:

toggle send rtcp events off fire_rtcp_events.
eval most common path first when checking flags.

src/include/switch_types.h

@@ -843,6 +843,7 @@ typedef enum {
 	SWITCH_RTP_FLAG_PASSTHRU,
 	SWITCH_RTP_FLAG_SECURE_SEND_MKI,
 	SWITCH_RTP_FLAG_SECURE_RECV_MKI,
+	SWITCH_RTP_FLAG_AUDIO_FIRE_SEND_RTCP_EVENT,
 	SWITCH_RTP_FLAG_VIDEO_FIRE_SEND_RTCP_EVENT,
 	SWITCH_RTP_FLAG_INVALID
 } switch_rtp_flag_t;