[clang-format] Proposal for clang-format to give compiler style warnings

relanding {D68554} with fixed lit tests, checked on Windows and MacOS

git-svn-id: svn://svn.chromium.org/llvm-project/cfe/trunk/tools/clang-format@374720 0b72dbe1-c17f-4bc7-b9db-2b4152be0356
2 files changed