Fix formatting and add a pipeline that runs the checker

[Oppen]

The title is self-descriptive. Many files fail the clang-format-check.sh, discouraging using clang-format.sh to keep the newer patches in shape.
Fixing is easy, a single commit per-file for easy revision, and I can do that easily.
The second part is about preventing getting to that state again. The pipeline should run clang-format-check.sh. As I'm not admin for the repo, I can only suggest it.

[Oppen]

Soooo, this actually can be done by me in a PR. I didn't know that.

[lemire]

@Oppen As far as GitHub actions, you can indeed propose something.

It makes little difference whether one is 'admin' or not, actually.