Make outbound Google Voice calls.

Make outbound Google Voice calls.

This patch allows for outbound Google Voice calls to be
dialed from Asterisk using chan_gtalk. Below is an example
dialstring.

exten -> blah,1,Dial(Gtalk/asterisk/+15552225555@voice.google.com,,)

In this example, 'asterisk' is the jabber.conf profile configured
to connect to your gmail account. In order to receive Google Voice
calls make sure to enable 'allowguest=yes' in gtalk.conf.

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@290973 65c4cc65-6c06-0410-ace0-fbb531ad65f3