Reload patch to improve 386 code

[Jeffrey A Law]

  In message < 199809052204.XAA14607@phal.cygnus.co.uk >you write:
  > > We actually have most of the stuff to implement this now.  We just need
  > > to set the alias set for such MEMs so that they have a different set
  > > than all the MEMs created before reload.
  > 
  > It's not quite that simple.  You also have to know that different stack
  > slots don't alias each other.
By setting the alias set, we disambiguate all the spill slots from
all the other pointers in the code.

We then let the existing base address tracking code disambiguate the
stack slots from each other.

jeff