Handle TMSI reallocation complete by printing the subscriber

It looks like that certain phones that send their old TMSI from
a different network and we assign them a new one with LOCATION
UPDATING ACCEPT will send us a TMSI Reallocation Complete. Print out
the the imsi.

diff --git a/src/gsm_04_08.c b/src/gsm_04_08.c
index aca4cf2..587bd39 100644
--- a/src/gsm_04_08.c
+++ b/src/gsm_04_08.c
@@ -562,8 +562,13 @@
 	case GSM48_MT_MM_STATUS:
 		DEBUGP(DMM, "MM STATUS: FIXME parse error cond.\n");
 		break;
-	case GSM48_MT_MM_CM_REEST_REQ:
 	case GSM48_MT_MM_TMSI_REALL_COMPL:
+		DEBUGP(DMM, "TMSI Reallocation Completed. Subscriber: %s\n",
+		       msg->lchan->subscr ?
+				msg->lchan->subscr->imsi :
+				"unknown subscriber");
+		break;
+	case GSM48_MT_MM_CM_REEST_REQ:
 	case GSM48_MT_MM_AUTH_RESP:
 	case GSM48_MT_MM_IMSI_DETACH_IND:
 		fprintf(stderr, "Unimplemented GSM 04.08 MM msg type 0x%02x\n",