Commit a8861b6cc removed packages/DOS but left a few traces of it
which broke the distcheck CI. Remove all traces.
Closes: #9971
Reviewed-by: Daniel Stenberg <daniel@haxx.se>
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
