This must have inadvertantly got merged in sometime as the code doesn't handle
this option, and configs/sip.conf.sample doesn't mention it as available. So
just remove it from the WARNING message
git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.0@169558 65c4cc65-6c06-0410-ace0-fbb531ad65f3