While we use rustfmt and clippy for Rust code, we never settled on a coding style for the C portions of the project (the init binary). This has caused the files to divert in style, and in some cases to have multiple styles mixed in. Let's settle on a coding style, based on LLVM with a few tweaks to make it reasonably close to what we were doing so far. We do this by adding a clang-format configuration file and formatting existing files. The next commit will extend the tests to ensure PRs adhere to the coding style in clang-format. Signed-off-by: Sergio Lopez <slp@redhat.com>