In addition to making it so attended transfers don't fail unnecessarily,

add some new options to control what happens when you hangup on an attended
transfer before the target extension answers the transferred channel.  You
can now have it send the transferee back to the transferer.
(issue #8413, patch from sergee with very minor modifications by me)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@62593 65c4cc65-6c06-0410-ace0-fbb531ad65f3