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
As that would indicate an illegal header. The fuzzer reached the assert
in unfold_value() proving that this case can happen.
Follow-up to c9b60f0053Closes#8939
Folded header lines will now get passed through like before. The headers
API is adapted and will provide the content unfolded.
Added test 1274 and extended test 1940 to verify.
Reported-by: Petr Pisar
Fixes#8844Closes#8899
