Add clang-formating for c sources and headers.

[vehre]

coverage on master

Summary of changes

Unify formatting of C sources utilizing a tool available on all platforms.

Rationale for changes

Editing the sources always lead to indentation and formatting getting ugly or I had to manually fix the formatting my IDE did. I therefore opted to use a tool (clang-format) that is widely available and can be configured to have the code look very similar to the previous version. Furthermore does is support partial formatting in IDEs, i.e. only code that is edited is reformatted.

Additional info and certifications

This pull request (PR) is a:

• Bug fix
• Feature addition
• Other, Please describe:

I certify that

• I certify that:
  • I have reviewed and followed the contributing guidelines
  • I will wait at least 24 hours before self-approving the PR to give another
    OpenCoarrays developer a chance to review my proposed code
  • I have not introduced errant white space (no trailing white space or white space errors may
    be introduced)
  • I have added an explanation of what these changes do and why they should be included
  • I have checked to ensure there aren't other open Pull Requests for the same change
  • I have you written new tests for these changes
  • I have successfully tested these changes locally
  • I have commented any non-trivial, non-obvious code changes
  • The commits are logically atomic, self consistent and coherent
  • The commit messages follow best practices
  • Test coverage is maintained or increased after this is merged

Code coverage data