Add ability to clone ao2 containers.
Occasionally there is a need to put all objects in one container also into
another container.
Some reasons you might need to do this:
1) You need to reconfigure a container. You would do this by creating a
new container with the new configuration and ao2_container_dup the old
container into it. Then replace the old container with the new. Then
destroy the old container.
2) You need the contents of a container to remain stable while operating
on all of the objects. You would do this by creating a cloned container
of the original with ao2_container_clone. The cloned container is a
snapshot of the objects at the time of the cloning. When done, just
destroy the cloned container.
Review: https://reviewboard.asterisk.org/r/1746/
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@357145
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