Recent CDR fixes moved execution of the 'h' exten into the bridging code, so variable...

Recent CDR fixes moved execution of the 'h' exten into the bridging code, so variables that were set after ast_bridge_call was called would not show up in the 'h' exten.  Added a callback function to handle setting variables, etc. from w/in the bridging code.  Calls back into a nested function within the function calling ast_bridge_call

(closes issue #13793)
Reported by: greenfieldtech

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@153181 65c4cc65-6c06-0410-ace0-fbb531ad65f3