Backport changes from llvm/.clang_tidy to clang/.clang_tidy configs

Summary: LLVM .clang_tidy seems to be more up-to-date.

Reviewers: alexfh, simark

Reviewed By: alexfh

Subscribers: simark, cfe-commits

Differential Revision: https://reviews.llvm.org/D44628

llvm-svn: 327984