/ added a ring timer so that an incoming call will termintate if it hasnt

/ been answered before the caller hangs up, and the telco doesnt provide a
/ loop-drop event on caller hang up.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@4787 65c4cc65-6c06-0410-ace0-fbb531ad65f3