move ran_conn declarations to new ran_conn.h

With the dawn of inter-BSC,MSC handover, adopting the MSC-A,-I,-T roles from
3GPP TS 49.008, the RAN connection shall soon be a neatly separated corner of
osmo-msc, so gravitate ran_conn decarations to files of matching name.

Also, the current chaos of API defined in files with mismatching/meaningless
names drives me crazy.

Change-Id: Ice31e6c43e46678538c65261f150c67e1d0845e5
diff --git a/include/osmocom/msc/vlr.h b/include/osmocom/msc/vlr.h
index 6e16903..1168c32 100644
--- a/include/osmocom/msc/vlr.h
+++ b/include/osmocom/msc/vlr.h
@@ -9,7 +9,7 @@
 #include <osmocom/gsm/gsm23003.h>
 #include <osmocom/gsm/gsm0808.h>
 #include <osmocom/gsm/gsup.h>
-#include <osmocom/msc/gsm_data.h>
+#include <osmocom/msc/ran_conn.h>
 // for GSM_NAME_LENGTH
 #include <osmocom/msc/gsm_subscriber.h>
 #include <osmocom/gsupclient/gsup_client.h>