new parameter 'R' to the Queue application

The 'R' argument stops moh and indicates ringing once the agent is
ringing.  This allows the person in the queue to know their call
is potentially about to be answered.

(closes issue #16384)
Reported by: haakon
Patches:
      new_app_queue.c.patch uploaded by haakon (license 880)
Tested by: haakon, loloski, dvossel


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@236304 65c4cc65-6c06-0410-ace0-fbb531ad65f3