scheduling problems again

[Jeffrey A Law]

  In message < 199801280510.VAA12134@kankakee.wrs.com >you write:
  > I'm not sure if I understand exactly where they can't go, but my guess
  > is you meant the below cases.  If I guessed right, can you put this
  > in, so that the people that stare at the machine ports in question,
  > can stare at the bogosity of the port as well.  The first step in
  > fixing a problem is identifying it.
They can't go in a peephole (since peepholes are performed after reload),
they can't go in output routines (since that happens after reload).

This patch doesn't catch them all, but it does note all the ones in 
peepholes, which is as good a start as any...

Though we really should fix dead_or_set_p.

jeff