AC_SUBST_FILE does look appealing. My changes were initially only going
to affect aclocal.m4 and config/post.in.

I will finish my work in my fashion - and will examine the use
of AC_SUBST_FILE - can one guarantee that the order of inclusion of files.
I also believe substitutions will not be made to the included files
(which would be nice). It would mean that we might need to generate
config/pre.in with all the substitutions - and then the rest of the files.
I guess this could be considered phase II.

	Ezra