[Users] Reformatting Carpet's source code

I've come to like to use a tool to automatically indent and format source code. This has several advantages -- the code has automatically a consistent style, indentation errors become obvious, and one doesn't have to spend time formatting the code manually while coding.

clang-format is the best such tool of which I'm aware. It's vastly better than e.g. GNU indent.

I propose to re-format Carpet's source code via clang-format.

Usually, changing the source code format is disruptive, since patches or local modifications won't apply cleanly any more. However, with clang-format, I don't think that this is an issue -- one can use clang-format on the modified code (e.g. a branch), which should eliminate gratuitous changes.

Please comment.

-erik