SourceForge projects can now choose between two hostnames, with .io and
.net ending. Both support HTTPS by default now. Opening the other variant
will perm-redirected to the one chosen by the project.
The .io -> .net redirection is done insecurely.
Let's update the URLs to point to the current canonical endpoints to
avoid any redirects.
Closes#9630
Add licensing and copyright information for all files in this repository. This
either happens in the file itself as a comment header or in the file
`.reuse/dep5`.
This commit also adds a Github workflow to check pull requests and adapts
copyright.pl to the changes.
Closes#8869
