Add an option, waitfordialtone, for UK analog lines which do not end a call

until the originating line hangs up.
(closes issue #12382)
 Reported by: one47
 Patches: 
       zap-waitfordialtone-trunk.080901.patch uploaded by one47 (license 23)
       zap-waitfordialtone-bra-1.4.21.2.patch uploaded by fleed (license 463)
 Tested by: fleed


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@159317 65c4cc65-6c06-0410-ace0-fbb531ad65f3