gsm48_tx_mm_auth_req(): support UMTS AUTN

To be able to do R99 UMTS authentication, we need to send along AUTN bytes in
the Authentication Request. Add autn parameter to gsm48_tx_mm_auth_req() and
conditionally append the R99 AUTN TLV to the Authentication Request message.

Change-Id: I0d644559088706aa06b42b9bfe1f8c21ca6fa4da
diff --git a/openbsc/src/libmsc/token_auth.c b/openbsc/src/libmsc/token_auth.c
index 95fd9b3..5af1e98 100644
--- a/openbsc/src/libmsc/token_auth.c
+++ b/openbsc/src/libmsc/token_auth.c
@@ -106,7 +106,7 @@
 			if (conn) {
 				uint8_t auth_rand[16];
 				/* kick the subscriber off the network */
-				gsm48_tx_mm_auth_req(conn, auth_rand, 0);
+				gsm48_tx_mm_auth_req(conn, auth_rand, NULL, 0);
 				gsm48_tx_mm_auth_rej(conn);
 				/* FIXME: close the channel early ?*/
 				//gsm48_send_rr_Release(lchan);
@@ -143,7 +143,7 @@
 	conn = connection_for_subscr(sms->receiver);
 	if (conn) {
 		/* kick the subscriber off the network */
-		gsm48_tx_mm_auth_req(conn, auth_rand, 0);
+		gsm48_tx_mm_auth_req(conn, auth_rand, NULL, 0);
 		gsm48_tx_mm_auth_rej(conn);
 		/* FIXME: close the channel early ?*/
 		//gsm48_send_rr_Release(lchan);