[SCCP MASQ] introduce stateful SCCP global title masquerading

WARNING: no timeouts have yet been implemented!
diff --git a/src/mgw_nat_usr.erl b/src/mgw_nat_usr.erl
index 562c07a..0743aad 100644
--- a/src/mgw_nat_usr.erl
+++ b/src/mgw_nat_usr.erl
@@ -37,6 +37,7 @@
 %% Callback functions of the OTP behavior
 
 init(Params) ->
+	sccp_masq:init(),
 	apply(sctp_handler, init, Params).
 
 handle_cast(stop, LoopData) ->