"groffer" Makefile case-sensitive

[Bernhard Fisseni]

Good morning,

When re-making CVS groff, I noticed a problem with the groffer setup:
There are two versions, perl and shell in the respectively named
directories, and the groffer Makefile uses PERL and SHELL file names,
which obviously cannot work on case-insensitive (if case-aware) file
systems (like HFS+ on a Mac).  Changing the temporary file names to
PERLFILE and SHELLFILE, everything works well, of course.

Cheers,
Bernhard