[PATCH,gfortran] constify a function

[Paul Brook]

> After reading and understanding what compare_case() does,
> I decide to clean up because several of the if statements
> could be collpased.
>
> 2004-12-30  Steven G. Kargl  <kargls@comcast.net>
>          * resolve.c (compare_case): Constify and cleanup

Applied with testcases.

Paul