When building the route set of ACKs for local UACs, only the reply is now

evaluated; this is insufficient, since replies to in-dialog requests normally
miss the route set. The patch fixes that: evals INVITE, if this was in-dialog;
otherwise, the reply (since the req. doesn't have yet complete route set).

Add support for the SASI if'ace, adding the implemenation for two more TM API
functions:
- t_get_canceled_ident(): returns the hash coordinates (bucket/index) of the
  transaction the currently processed CANCEL is targeting
- ack_local_uac(): allow generating the ACKs for 2xx'ed locally originated
  INVITEs - new headers and body can now also be appended to it.

Fully closes #SER-346.

modules_s/dialog/serialize_dlg.c

@@ -309,7 +309,7 @@ int serialize_dlg(sstream_t *ss, dlg_t *dlg)
 	if ((res == 0) && (is_input_sstream(ss))) {
 		/* tmb.w_calculate_hooks(dlg); */
 		res = tmb.calculate_hooks(dlg);
-		if (res != 0) {
+		if (res < 0) {
 			ERROR_LOG("error during calculate_hooks (%d)!\n", res);
 		}
 	}