[Serusers] t_uac_dlg to nated UAS

[Juha Heinanen]

if i use t_uac_dlg fifo command to send an invite request to a UAS that
is behind NAT, t_uac sends ACK to the private contact address of 200
OK.

in order fix the contact address in 200 OK, i should be able to somehow
tell to t_uac_dlg that it should set a t_on_reply for the transaction.
i didn't find any t_uac_dlg parameter for that purpose.  

perhaps there is some other way to get the contact address fixed?

-- juha