eo: Remove lock from efl_super

eo: Remove lock from efl_super

I've always really disliked this lock. If someone calls a non-eo
function by accident with efl_super() then you'll most likely end
up in a deadlock.

This adds the cur_klass pointer to the object itself, exploiting
the fact that we have 8 bytes of padding (on 64 bits, at least).

Also, this opens the door to efl_cast() which would be similar to
efl_super() except that only a dynamic cast is done, not a call
to the parent function.

make benchmark shows a performance improvement, surprisingly.

This is a bit experimental. See also the following commit (efl_cast)