[refactor] Move clang-rename into the clang repository The core engine of clang-rename will be used for local and global renames in the new refactoring engine, as mentioned in http://lists.llvm.org/pipermail/cfe-dev/2017-June/054286.html. The clang-rename tool is still supported but might get deprecated in the future. Differential Revision: https://reviews.llvm.org/D34696 llvm-svn: 306840 GitOrigin-RevId: 4abbd92bf4c830549ff5536de9aa821012d76491