Add member_{add,del} as smart callbacks.

Add member_{add,del} as smart callbacks.

On the let's break 'em all bandwagon, add the two callbacks (or
virtuals if you like the name) so we can know when some object is
attached or detached as a member of our object, this will help
eliminate confusing and duplicate functions like
evas_object_smart_clipped_smart_add().

Please recompile *ALL* your libs and applications that depend on Evas
and Smart Objects, like ETK.

git-svn-id: svn+ssh://svn.enlightenment.org/var/svn/e/trunk/evas@37084 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33