Reload patch to improve 386 code

[Joern Rennecke]

> > Then again inheritance happens just before we start emitting the
> > reload insns themselves, so maybe it doesn't conflict with your code.
> 
> It really shouldn't. Inheritance only looks at the insns that reload is
> already done with, and the one currently being processed.  For those
> which reload has completed, the register life information calculated by
> my patch is never referenced again, so the inheritance code can do
> whatever it wants to them.

You'll have to add some code to tell the inheritance code when a reload
register becomes unavailable where it becomes used by a pseudo.