Installed header files

[Russ Allbery]

I've just committed a few changes that will make it much easier to
eventually install some of INN's header files (everything in include/inn)
and which should also improve our ability to use a real bool if the
compiler provides one.

The plan is to have three frequently-used headers in inn:

    inn/config.h        All of the stuff currently in config.h that isn't
                        autoconf-generated.  This is the header file that
                        users may want to edit before compiling.

    inn/defines.h       Like it is now, various utility macros.  Includes
                        <inn/system.h> and included probably by every
                        non-trivial header file in inn/*, for BEGIN_DECLS
                        and END_DECLS if nothing else.

    inn/system.h        Automatically generated from config.h, containing
                        the autoconf results.  Currently this is just
                        what's used by the existing inn/* headers, but in
                        time this should also include all the
                        user-specified configure parameters that an
                        application may find interesting.

I'm not entirely satisfied with the name <inn/config.h>, so if anyone has
any better ideas, let me know.  It's not a bad name, although potentially
confuseable with an autoconf-output header.

config.h will just include all three of these headers, so the rest of INN
can continue to use the stuff in them by just including config.h as it
does now.  config.h won't be an installed header, though (too much chance
of it conflicting with autoconf results from other packages).

inn/system.h is being generated by an awk script that I *think* is
portable, but let me know if you run into any problems.  I haven't written
a lot of portable awk, but I didn't want to require Perl for that (for no
particularly good reason, but hey -- maybe someone will find the idea
useful for their own package).

There's still a lot of work to do before we'll be ready to start
installing header files (a bunch of the headers in include need to be
cleaned up and moved to include/inn, for one), but now the basic
mechanisms are in place.

-- 
Russ Allbery (rra at stanford.edu)             <http://www.eyrie.org/~eagle/>