mgcp: Introduce multiple virtual trunks

A virtual trunk is identified by a virtual domain name.
diff --git a/include/ss7_vty.h b/include/ss7_vty.h
index a0368bd..da599e5 100644
--- a/include/ss7_vty.h
+++ b/include/ss7_vty.h
@@ -28,6 +28,7 @@
 enum ss7_vty_node {
 	MGCP_NODE = _LAST_OSMOVTY_NODE + 1,
 	TRUNK_NODE,
+	VTRUNK_NODE,
 	CELLMGR_NODE,
 	SS7_NODE,
 	LINKSETS_NODE,