MMD with native type right operand

[Leopold Toetsch]

I know, I've asked this question some time ago, and implemented 
MMD_ADD_INT and friends. But I can't reproduce the full rationale WRT 
dispatching of these methods.

  add Px, Py, Iz
can clearly use only the left hand operand Py. So it's not a real MMD, 
the right hand operand is always a plain integer. This would indicate 
that it should be a vtable call.

OTOH
  add Px, Py, Pz
is an MMD method. Having two different dispatch schemes seems a bit 
undesirable for such similar operations. But two schemes are needed 
anyway for overriding e.g. set_integer, which is a vtable.

So I'm quite unsure, what's right.
leo