Fix several problems with ast_bridge_add_channel().

* Fix locking problems.  ast_bridge_move() locks two bridges.  To do that,
deadlock avoidance must be done.  Called bridge_move_locked() instead.

* Fix inconsistency in the bridge dissolve check callers.  The original
caller has already removed the channel from the bridge.  The new caller
has not removed the channel from the bridge.  Reverted
bridge_dissolve_check() and added bridge_dissolve_check_stolen() to be
used by the new caller on the original bridge after the channel is moved
to the new bridge.

* Fix memory leak of features if the added channel was already in a
bridge.

* Fix incorrect call to ast_bridge_impart().

* Renamed bridge_chan to yanked_chan.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@392953 65c4cc65-6c06-0410-ace0-fbb531ad65f3