[reSIProcate] DUM: Enqueue conference call results

["Derek MacDonald" <derek@xxxxxxxx>]

So, here are the changes that I will make next week as a result of the
enqueue discussion.

1.) makeCancel will migrate to DialogSet, CANCEL/provisional responses to
re-invites will be ignored. Calling end on a dialog will call the DialogSet
level cancel if appropriate.

2) Users can start a new Invite transaction even if they are waiting for the
ACK of another invite transaction as a UAS.  Ie -- I can put you on hold
even though I'm still retransmitting the 200. 

3.) There will be a new callback to indicate that no ACK was received for a
particular transaction, rather than the dubious overloaded 408.

4.) ackConnection will go away. Call setAnswer & send() instead.  If the SDP
state machine does not require an answer, the ACK will be sent immediately
when the 200 is received.  ACK adornment must be accomplished through
onReadyToSend.

send with no parameters is the new enqueue...this will eventually be
extended to support PRACK/180rel/etc.

5.) In Dialog requests that are generic to both subscription & invite
dialogs will migrate to DialogUsage, all other will be added to
InviteSession.  Only one in-dialog requests at a time will be
allowed(exception).  Scott, I'll talk with you about how this should all be
implemented.

--Derek