Change the behavior of ao2_link(). Previously, in inherited a reference.
Now, it automatically increases the reference count to reflect the reference
that is now held by the container.
This was done to be more consistent with ao2_unlink(), which automatically
releases the reference held by the container. It also makes it so it is
no longer possible for a pointer to be invalid after ao2_link() returns.
git-svn-id: http://svn.digium.com/svn/asterisk/branches/1.4@90348 614ede4d-c843-0410-af14-a771ab80d22e