[PATCH] Use LLVM when the buffer isn't associated with a file.

[Ahmed Charles]

  I just noticed that if you have a buffer that has no file, that it will result in clang-format printing stuff to stderr, which means that the python will tell vim that there was an error. I'd like to make that a more useful error or have it not happen, but preferably without breaking anything. Does that make sense?

http://llvm-reviews.chandlerc.com/D3019