mgw: Add first tests for testing RTP streams

The existing MGW tests were entirely on the MGCP side.  Let's start
some tests that exchange RTP frames with the MGW and validate that
the MGW can actually act on what is configured via MGCP.

Change-Id: If620d5f8927d0e3584e90a7a8f785c6fdd7c2d17
diff --git a/library/MGCP_Templates.ttcn b/library/MGCP_Templates.ttcn
index 9e32a34..e509da8 100644
--- a/library/MGCP_Templates.ttcn
+++ b/library/MGCP_Templates.ttcn
@@ -124,6 +124,16 @@
 		sdp := *
 	}
 
+	template MgcpResponse tr_MDCX_ACK := {
+		line := {
+			code := "200",
+			trans_id := ?,
+			string := "OK"
+		},
+		params := *,
+		sdp := ?
+	}
+
 	template MgcpResponse ts_MDCX_ACK(MgcpTransId trans_id, MgcpConnectionId conn_id, template SDP_Message sdp := omit) := ts_CRCX_ACK(trans_id, conn_id, sdp);
 
 	/* have a function that generates a template, rather than a template in order to handle