astobj2: Additional refactoring to push impl specific code down into the impls.

Move some implementation specific code from astobj2_container.c into
astobj2_hash.c and astobj2_rbtree.c.  This completely removes the need for
astobj2_container to switch on RTTI and it no longer has any knowledge of
the implementation details.

Also adds AO2_DEBUG as a new compile option in menuselect which controls
astobj2 debugging independently of AST_DEVMODE and REF_DEBUG.

Tested by: George Joseph
Review: https://reviewboard.asterisk.org/r/3593/
........

Merged revisions 416806 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@416807 65c4cc65-6c06-0410-ace0-fbb531ad65f3