stp: Add TC_ipa_to_m3ua_ni()

This tests sets a non-zero default network-indicator in the ss7 instance
and then performs an IPA -> M3UA translation while checking if the M3UA
side now uses the specified default network-indicator (NATIONAL).

Change-Id: Id4f9d0ff67e114a119ab032d44ac0dfd34f5c402
Related: SYS#5421
diff --git a/library/M3UA_Templates.ttcn b/library/M3UA_Templates.ttcn
index 5881b40..3667ca0 100644
--- a/library/M3UA_Templates.ttcn
+++ b/library/M3UA_Templates.ttcn
@@ -17,6 +17,9 @@
 
 const OCT1 c_M3UA_VERSION := '01'O;
 
+const OCT1 c_M3UA_NI_NATIONAL := '02'O;
+const OCT1 c_M3UA_NI_INTERNATIONAL := '00'O;
+
 const OCT2 c_M3UA_ST_T_STATE_CHG := '0001'O;
 const OCT2 c_M3UA_ST_I_RESERVED := '0001'O;
 const OCT2 c_M3UA_ST_I_AS_INACTIVE := '0002'O;