don't use tone generation for DTMF if the channel driver only supports...

don't use tone generation for DTMF if the channel driver only supports begin/end (will need more work to translate non-variable events into begin/end events)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@8852 65c4cc65-6c06-0410-ace0-fbb531ad65f3