scheduling problems again

[amylaar@cygnus.co.uk]

> No.  I'd just change it to ignore REG_DEAD notes after reload instead of
> aborting.  There's still cases where it would be useful if it ignored such
> notes.

Actually, REG_DEAD notes still have some meaning after reload:  they mean
that the register dies somewhere in the current basic block.
Thus, when this is good enough, the current definition of dead_or_set_p
is useful.