* Moved message deletion into the CtdlRoomAccess() API. The

* Moved message deletion into the CtdlRoomAccess() API.  The
  old function DoIHavePermissionToDeleteMessagesFromThisRoom() is now a
  simple wrapper around CtdlRoomAccess().
* This gives us the ability to query arbitrary room/user combinations, not
  just "this user, this room."  It also paves the way for the ability to
  grant "delete privileges" to any user for any room in the future.
* IMAP ACL now uses this feature to set or clear the "t" flag.  Observed
  that Thunderbird now activates or deactivates the Delete button for each
  folder based on the "t" flag.