creating branch for invite session nit queueing changes

git-svn-id: https://svn.resiprocate.org/rep/resiprocate/branches/b-nitqueuing@7552 ddefafc4-47db-0310-ae44-fa13212b10f2
-patch to provide queuing of InviteSession refer, message, and info requests

git-svn-id: https://svn.resiprocate.org/rep/resiprocate/branches/b-nitqueuing@7553 ddefafc4-47db-0310-ae44-fa13212b10f2