mgcp: Introduce a trunk config for multiple trunks.

A trunk will always have 32 endpoints to be used and we allow
a sparse allocation of endpoints.
diff --git a/openbsc/src/common_vty.c b/openbsc/src/common_vty.c
index 25ab3c0..84375a2 100644
--- a/openbsc/src/common_vty.c
+++ b/openbsc/src/common_vty.c
@@ -86,6 +86,9 @@
 	case MSC_NODE:
 		vty->node = GSMNET_NODE;
 		break;
+	case TRUNK_NODE:
+		vty->node = MGCP_NODE;
+		break;
 	default:
 		vty->node = CONFIG_NODE;
 	}
@@ -154,6 +157,10 @@
 	case MSC_NODE:
 		vty->node = GSMNET_NODE;
 		break;
+	case TRUNK_NODE:
+		vty->node = MGCP_NODE;
+		vty->index = NULL;
+		break;
 	default:
 		break;
 	}
@@ -175,6 +182,7 @@
 	case TRX_NODE:
 	case TS_NODE:
 	case MGCP_NODE:
+	case TRUNK_NODE:
 	case GBPROXY_NODE:
 	case SGSN_NODE:
 	case NS_NODE: