[PATCH]: Handle lonely CC0 setter in sched-deps.c

[Paolo Bonzini]

> While testing scheduling for ColdFire/m68k I noted ICE in sched-deps.c. 
>  The cause was that scheduler dependency analyzer couldn't handle 
> CC0-user instruction, that didn't have CC0-setter before the user.
> 
> The origin of this, somewhat strange, case is seqabstr pass, that 
> unified code for setting CC0 from several blocks into a pseudo-routine. 
>  So now code in the pseudo-routine sets CC0 and then jumps back to 
> CC0-user.

The fix is to not break the CC0 setter and user in seqabstr (which *is* 
in 4.3 too, but very broken).  The fact that setters and users cannot be 
separated, is one of the reasons why CC0 is deprecated.

Paolo