* mod_dlg saves the initial INVITE to DSMSession::last_req
* set connect_session to 0 with set(connect_session=0)
  if you want to reply with other than the standard 200 OK 
  to initial INVITE received.

 reply to the request in DSMSession::last_req 
 (usually INVITE, if not yet replied) with code and reason
 * sets $errno (arg,general)

dlg.acceptInvite([code, reason]);
 e.g. dlg.acceptInvite(183, progress);
 * sets $errno (arg,general)
 accept audio stream from last_req (INVITE), and reply with 200 OK (default)
 or code, reason
 send BYE. useful for example for continuing processing after call has ended.
 * sets $errno (general)

dlg.connectCalleeRelayed(string remote_party, string remote_uri)
 like B2B.connectCallee() but for relayed INVITEs, i.e. for executing in 
 invite run (run_invite_event=yes and transition "on INVITE" START - invite -> runinvite;)

dlg.dialout(string arrayname)
  dial out a new call
  simple format/mandatory:
   arrayname_caller   caller user
   arrayname_callee   callee user
   arrayname_domain   domain caller and callee
   arrayname_app      application to execute

   arrayname_r_uri     INVITE request URI
   arrayname_from      From
   arrayname_from_uri  From URI (only internally used)
   arrayname_to        To
   arrayname_auth_user authentication user
   arrayname_auth_pwd  authentication pwd
   arrayname_ltag      ltag for new call
   arrayname_hdrs      headers for new call

  returns $arrayname_ltag and sets ERRNO.