misc: Move handover_logic.c into the libbsc.a

We are implementing the intra BSC handover so we should have the
code in the BSC as well.
diff --git a/openbsc/src/gsm_subscriber_base.c b/openbsc/src/gsm_subscriber_base.c
index c06b1ce..b373523 100644
--- a/openbsc/src/gsm_subscriber_base.c
+++ b/openbsc/src/gsm_subscriber_base.c
@@ -112,6 +112,14 @@
 	}
 }
 
+char *subscr_name(struct gsm_subscriber *subscr)
+{
+	if (strlen(subscr->name))
+		return subscr->name;
+
+	return subscr->imsi;
+}
+
 struct gsm_subscriber *subscr_alloc(void)
 {
 	struct gsm_subscriber *s;