Fixes several files incorrectly stated a different license from the actual project, as well as the copyright headers included in all files. This change has no effect on the licensing terms, it should clear up a bit of confusion by contributors. Plus the files get a bit smaller, and we have less duplicated information across the entire project.
Overall the project is GPLv2 if not built with Qt, and GPLv3 if it is built with Qt. There are no parts licensed under a different license, all have been adapted from other compatible licenses into GPLv2 or GPLv3.
- Updates all workflow actions to the latest major version where possible.
- Updated GCC to version 10 on Ubuntu.
- Update Clang to version 14 on Ubuntu.
- Removed CodeQL as it turned out to be completely useless.
- Updated validation script.
- Updated build script
