RFC: Move forwarding ptr into the object

[Andrew Haley]

On 27/09/16 14:18, Roman Kennke wrote:
> Great work! Some comments...

I'm a little bit worried that changing object layout in such a
fundamental way might lead to objections merging this, and might
break more things.  At the moment almost everything which gets
an OOP knows the object layout.  Maybe we're just setting ourselves
up for more pain.

Andrew.