evas: Override del() for evas objects

evas: Override del() for evas objects

This makes EAPI evas_object_del() and EO API efl_del() work the same on
evas objects, i.e. a del() implies an immediate call to hide() and mark
the object as "delete_me".

If the refcount remains > 0 the object won't be actually deleted, thus
EFL_EVENT_DEL won't be triggered. I think it would probably be a good
idea to have a new event "del,request", to signal reference owners that
this object "wants" to die.

Ping @raster @zmike