Run clang-tidy's modernize-use-override checker. This checker must have
issues in version 3.8. It has way too little matches. And it adds
override to destructors. Revert the changes on the destructors and
change override to CM_OVERRIDE.
Use clang-tidy's readability-simplify-boolean-expr checker.
After applying the fix-its, revise all changes *very* carefully.
Be aware of false positives and invalid changes.
