We need to get rid of configure.ac stub

[Ben Wing]

> recently I have updated the xemacs packages for the next SuSE 
> Linux distribution to XEmacs 21.5.18. I'll attach our current 
> autoconf patch which is against XEmacs 21.5.18 in the hope 
> that it is helpful.
> 
> I believe most of this patch is originally by Andreas Schwab 
> <schwab at suse.de> (added to CC:).

Mike -- this patch looks good, but I notice you have deleted some of the
code to generate both Makefile and GNUMakefile; now it appears that the
plain Makefile is generated with -DUSE_GNU_MAKE.  Could you fix this?

ben