Upgrade the build system

• add ./autogen.sh to re-generate the Autotools files;
• remove the automatically generated Autotools file from the repo;
• set --enable-maintainer-mode=yes by default;
• copy the Libtool patches from YAXT to simplify the generation of dynamic libraries;
• minor refactoring.

changed the description

@jahns, since we use reuse in our CI for checking the licenses, I had to make a decision on the copyright and license tags for the contrib patches and README.txt files:

Files: contrib/*/README.txt
Copyright: 2024 Thomas Jahns <jahns@dkrz.de>
License: CC-BY-4.0

Files: contrib/*.patch
Copyright: 2024 Thomas Jahns <jahns@dkrz.de>
License: GPL-2.0-or-later WITH Libtool-exception

I chose GPL-2.0-or-later WITH Libtool-exception for the patch files since it is the same license as for the ltmain.sh file they patch.

Please, let me know if it's fine with you.

That's all good, go ahead.

mentioned in merge request !42 (merged)

@m214089, FYI

Thanks!

merged