eina: add Eina_Object API.

eina: add Eina_Object API.

This API is what could be used by all EFL library for their exposed
type (Evas_Object, Ecore_Timer, Ecore_Animator, Eio_File, ...). The
purpose of Eina_Object is to provide an "obscure" pointer that is
infact an ID with a generation count that will never be dereferenced
directly.
   This provide the benefit of always accessing a living object
with 1/256 chance to being the expected generation of it, that will
always be of the right type.
   It also provide asynchronous repacking ability (still highly
inefficient, but not really hard to improve), simple inheritance
with constructor/destructor and link between object.

All this implementation is highly open for comment, idea, review,
fix and change. I didn't got the time to write a sample test right
now. Maybe will come tomorrow. Same for docs.

git-svn-id: svn+ssh://svn.enlightenment.org/var/svn/e/trunk/eina@58562 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33