Making libunistring optional

[Ludovic Courtès]

Hello,

Here’s an attempt to “reduce the number of dependencies” of Guile.  The
approach, as suggested by Bruno Haible, uses Gnulib’s
‘libunistring-optional’ module, along with the 22 (!) unistring modules
that provide the functionality we need.

When libunistring is available, it is used as before; when it’s not,
those modules are built and linked into libguile.

I had become convinced that this is a good idea, and a simple way to
make our user’s lives easier.  Yet, this adds 184 source files to the
tarball (would be more if we included tests), so I’d like to hear
opinions.

Thoughts?

Ludo’.

0001-Use-Gnulib-s-libunistring-optional-and-22-unistring-.patch.gz
Description: the patch