Minor cleanup in configure.in

[DJ Delorie]

kenner@vlsi1.ultra.nyu.edu (Richard Kenner) writes:
> Tue Feb 13 07:52:04 2001  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
> 
> 	* configure.in: Use "have_gnat" variable, not "gnat".
> 	* configure: Regenerated.

OK.