Make use of REUSE 3.2 and REUSE.toml

[mxmehl]

REUSE received a significant update of its specification. This version allows for a new way to communication licensing and copyright of files that cannot be annotated directly: REUSE.toml.

This PR migrates the deprecated way of doing so (dep5) to this improved way. It would also allow for adding multiple REUSE.toml files, e.g. one separate in /docs/ and /tests/, but I figured this "central" approach might have it advantages for the curl project.

Two FAQ items on REUSE.toml if you're interested, one about bulk licensing, the other about additional licensing info.

Here is the full changelog of REUSE 3.2.

[mxmehl]

I noticed that scripts/copyright.pl also makes use of the dep5 file.

I wonder whether the file is actually still needed. If you wanted to learn whether you're compliant, reuse lint is the way to go. If you need to know which file has which license/copyright, reuse lint -j may help.

[bagder]

I noticed that scripts/copyright.pl also makes use of the dep5 file. I wonder whether the file is actually still needed.

I think it has outlived its purpose now. You can probably remove it in this PR.

[mxmehl]

I think it has outlived its purpose now. You can probably remove it in this PR.

Excellent. Done and updated the documentation as well.

The PR seems to be ready content-wise. If you agree to its changes I may also clean it up if wanted, unless you intend to squash everything anyway.

[bagder]

Thanks!