Add SGs Interface

Add an SGs interface (3GPP TS 29.118) to osmo-msc in order to support
SMS tunneling and Circuit Switched Fallback (CSFB)

Change-Id: I73359925fc1ca72b33a1466e6ac41307f2f0b11d
Related: OS#3615
diff --git a/include/osmocom/msc/Makefile.am b/include/osmocom/msc/Makefile.am
index 13ac166..408d710 100644
--- a/include/osmocom/msc/Makefile.am
+++ b/include/osmocom/msc/Makefile.am
@@ -23,11 +23,15 @@
 	a_reset.h \
 	ran_conn.h \
 	rrlp.h \
+	sgs_iface.h \
+	sgs_server.h \
+	sgs_vty.h \
 	signal.h \
 	silent_call.h \
 	smpp.h \
 	sms_queue.h \
 	transaction.h \
 	vlr.h \
+	vlr_sgs.h \
 	vty.h \
 	$(NULL)