Autoconf macro for using Guile

[Jim Blandy <jimb@red-bean.com>]

I'm interested in people's comments on this (should be in tomorrow
morning's snapshots):


** Use the GUILE_FLAGS macro in your configure.in file to find Guile.

If you are using the GNU autoconf package to configure your program,
you can use the GUILE_FLAGS autoconf macro to call `guile-config'
(described above) and gather the necessary values for use in your
Makefiles.

The GUILE_FLAGS macro expands to configure script code which runs the
`guile-config' script, to find out where Guile's header files and
libraries are installed.  It sets two variables, marked for
substitution, as by AC_SUBST.

  GUILE_CFLAGS --- flags to pass to a C or C++ compiler to build
    code that uses Guile header files.  This is almost always just a
    -I flag.

  GUILE_LDFLAGS --- flags to pass to the linker to link a
    program against Guile.  This includes `-lguile' for the Guile
    library itself, any libraries that Guile itself requires (like
    -lqthreads), and so on.  It may also include a -L flag to tell the
    compiler where to find the libraries.

GUILE_FLAGS is defined in the file guile.m4, in the top-level
directory of the Guile distribution.  You can copy it into your
package's aclocal.m4 file, and then use it in your configure.in file.

If you are using the `aclocal' program, distributed with GNU automake,
to maintain your aclocal.m4 file, the Guile installation process
installs guile.m4 where aclocal will find it.  All you need to do is
use GUILE_FLAGS in your configure.in file, and then run `aclocal';
this will copy the definition of GUILE_FLAGS into your aclocal.m4
file.