pbx_dundi: Add PJSIP support.

Adds PJSIP as a supported technology to DUNDi.

To facilitate this, we now allow an endpoint to be specified
for outgoing PJSIP calls. We also allow users to force a specific
channel technology for outgoing SIP-protocol calls.

ASTERISK-28109 #close
ASTERISK-28233 #close

Change-Id: I2e28e5a5d007bd49e3df113ad567b011103899bf
(cherry picked from commit b33f92cbb5)

include/asterisk/dundi.h

@@ -59,6 +59,8 @@ enum {
 	DUNDI_PROTO_SIP  = 2,
 	/*! ITU H.323 */
 	DUNDI_PROTO_H323 = 3,
+	/*! PJSIP */
+	DUNDI_PROTO_PJSIP = 4,
 };
 
 enum {