new_ia32 branch: kill constrain_asm_operands

[Bernd Schmidt]

> > This merges another change that's missing from the new ia32 branch.
> > OK to install?
> 
> No, I'd rather be merging new ia32 into mainline.  While the stack
> alignment merge into the backend files is important so that we don't
> lose anything, such generic changes are not.

I was under the impression we were going to replace the ia32 specific parts
(including reg-stack.c) in the mainline with the new ones.

> If I start pulling out individual generic changes from new_ia32_branch,
> would you be willing to review them?  Given that I wrote most of them
> in the first place, I want another set of eyes on it before it goes
> into mainline.

Yes, I can do that.

Bernd