Update documentation as to the behavior of AGI in 1.6.0 and higher. Also, add

an OOB message that answers the question of, if AGI no longer shuts down the
connection on hangup, how will FastAGI know when to stop processing the call?


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@136859 65c4cc65-6c06-0410-ace0-fbb531ad65f3