Ignore-this: c5960a8330904eae5a1428158e4498c7

If media is enabled, stack autoacks 2XX responses to re-INVITEs unless
NUTAG_AUTOACK(0) is set on handle.

Also documenting NUTAG_AUTOACK() behaviour with re-INVITEs.

darcs-hash:20090512160519-db55f-4f5ff1650f8a633c3856f220e72bd5cec55b931d.gz