stop installing config.h for 3.2

[John W. Eaton]

I think it is time we stopped installing the complete config.h file,
at least with the name "config.h".  Instead, we should arrange for
configure to generate a config.h file with the typical autoconf
macros, and also a separate octave-config.h file that includes macros
specific to Octave that are required by other header files that we
install.  I think many of the current macros that are defined in
config.h are only used internally in .cc files, so this should make
the "octave-config.h" file much smaller than the config.h file is
currently, and also avoid potential conflicts for people who are
writing .oct files that needs a separate config.h file.

I think I will have time to attempt this change in the next few days.

Comments?

Thanks,

jwe