change some identifiers from u_int64_t to unsigned long long

makes printf much easier on 64bit platforms...
diff --git a/openbsc/include/openbsc/gsm_data.h b/openbsc/include/openbsc/gsm_data.h
index 94a7081..c3ea45d 100644
--- a/openbsc/include/openbsc/gsm_data.h
+++ b/openbsc/include/openbsc/gsm_data.h
@@ -416,7 +416,7 @@
 #define SMS_HDR_SIZE	128
 #define SMS_TEXT_SIZE	256
 struct gsm_sms {
-	u_int64_t id;
+	unsigned long long id;
 	struct gsm_subscriber *sender;
 	struct gsm_subscriber *receiver;