[PATCH] clang-format: allow _clang-format as an alternative config file name

[Hans Wennborg]

  > Note that you have one mention of _clang_format in the description and one in the code, and everywhere else afaict it's _clang-format. Please decide on one ;)

  Well spotted. I'll fix that before committing.

http://llvm-reviews.chandlerc.com/D1629