Add global ao2 array container.

Add global ao2 array container.

Global ao2 objects must always exist after initialization because there is
no access control to obtain another reference to the global object.

It is expected that module configuration could use these new API calls to
replace an active configuration parameter object with an updated
configuration parameter object.

With these new API calls, the global object could be replaced, removed, or
referenced without the risk of someone using a stale global object
pointer.

Review: https://reviewboard.asterisk.org/r/1824/

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@360627 65c4cc65-6c06-0410-ace0-fbb531ad65f3