Convert SDLOSXCAGuard files to UTF-8

[MaddTheSane]

Description

This simply coverts the files SDLOSXCAGuard.c and SDLOSXCAGuard.h from Mac OS Roman to UTF-8, quieting an issue with Clang about "invalid UTF-8 in comment."

Manual testing

I don't perceive this having any impact to any actual code, but might make the Apple license in those files more readable.

Checklist

I have:

• followed the project's contributing guidelines and code of conduct.
• performed a self-review of my code.
• commented on the particularly hard-to-understand areas of my code.
• split my work into well-defined, bisectable commits, and I named my commits well.
• applied the appropriate labels (bug, enhancement, refactoring, documentation, etc.)
• checked that all my commits can be built.
• confirmed that my code does not cause performance regressions (e.g., by running the Quake benchmark).
• added unit tests where applicable to prove the correctness of my code and to avoid future regressions.
• made corresponding changes to the documentation or the website according to the documentation guidelines.
• locally verified my website or documentation changes.

[kcgen]

Thanks for the fix, @MaddTheSane -- indeed, those copyright and apostrophe characters previously were shown as broken in my text editors.