Patch to equiv_constant in cse.c

[Jeffrey A Law]

  In message < 199810121827.LAA14569@elmo.cygnus.com >you write:
  > Hi,
  > 
  >   I would like to submit the enclosed patch to cse.c.  The patch fixes
  > a problem for the m32r toolchain when equiv_constant() calls
  > gen_lowpart_if_possible() which then returns NULL.  Without this patch
  > the code does not check for a NULL value. 
  > 
  > Cheers
  > 	Nick
  > 
  > 
  > Mon Oct 12 11:25:26 1998  Nick Clifton  <nickc@cygnus.com>
  > 
  > 	* cse.c (equiv_constant): Check for NULL return from
  > 	gen_lowpart_if_possible().
Looks good to me.

jeff