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/Makefile.am b/include/osmocom/msc/Makefile.am
index 28e4b14..9fa58c7 100644
--- a/include/osmocom/msc/Makefile.am
+++ b/include/osmocom/msc/Makefile.am
@@ -22,6 +22,7 @@
 	msc_mgcp.h \
 	a_reset.h \
 	osmo_msc.h \
+	ran_conn.h \
 	rrlp.h \
 	signal.h \
 	silent_call.h \