ChanSpy: Add ability to specify channel uniqueids as well as channel names.

* Made ChanSpy accept a channel uniqueid or a fully specified channel name
as the chanprefix parameter if the 'u' option is specified.

(closes issue AFS-42)

Review: https://reviewboard.asterisk.org/r/3160/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@407033 65c4cc65-6c06-0410-ace0-fbb531ad65f3