BSSMAP_Templates: Make ts_BSSAP_DTAP usable

A send template with '?' is broken.  Also, allow caller to specify DTAP
payload as well as optionally a DLCI.

Change-Id: I641ee8ce5e5ae70b514342cf68cdc79b1926c4d0
diff --git a/library/BSSMAP_Templates.ttcn b/library/BSSMAP_Templates.ttcn
index 2a9cef7..49844e7 100644
--- a/library/BSSMAP_Templates.ttcn
+++ b/library/BSSMAP_Templates.ttcn
@@ -114,13 +114,13 @@
 	}
 }
 
-template PDU_BSSAP ts_BSSAP_DTAP := {
+template PDU_BSSAP ts_BSSAP_DTAP(octetstring dtap, template OCT1 dlci := omit) := {
 	discriminator := '1'B,
 	spare := '0000000'B,
-	dlci := omit,
+	dlci := dlci,
 	lengthIndicator := 0,	/* overwritten by codec */
 	pdu := {
-		dtap := ?
+		dtap := dtap
 	}
 }