patch for update_flow_info REG_WAS_0

[Jeffrey A Law]

  In message < 199802130030.AAA24740@phal.cygnus.co.uk >you write:
  > update_flow_info tried in vain to find the new setter for a (mem:DI ...
  > value after this was split into two memory accesses...
  > 
  > Fri Feb 13 00:25:02 1998  J"orn Rennecke <amylaar@cygnus.co.uk>
  > 
  > 	* sched.c (update_flow_info, REG_WAS_0): Ignore if setting insn
  > 	was deleted.
One might argue that the note should have been removed when the
insn was deleted.  Can you look into that?

jeff