Merge in the bridge_construction branch to make the system use the Bridging API.

Breaks many things until they can be reworked.  A partial list:
chan_agent
chan_dahdi, chan_misdn, chan_iax2 native bridging
app_queue
COLP updates
DTMF attended transfers
Protocol attended transfers


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@389378 f38db490-d61c-443f-a65b-d21fe96a405b