jump.c patch

[Jeffrey A Law]

  In message < 199807042113.WAA07158@wildcat.demon.co.uk >you write:
  > I was running a recent version of the compiler to which I had
  > added some basic runtime checking of rtl expression types in the
  > rtl access macros.
Any chance we can get you to donate that code?  We'd like to have something
like that to catch these kinds of problems on a more regular basis.

It would probably be significant enough to need a copyright assignment
if you haven't already done one.

  > Sat Jul  4 22:10:46 BST 1998	Alasdair Baird	<alasdair@wildcat.demon
  > .co.uk>
  > 
  >     jump.c (jump_optimize) Check for CONST_INT before using INTVAL.
Thanks!  Installed.

jeff