Run ClangTidy tests in all C++ language modes
I inspected every test and did one of the following:
- changed the test to run in all language modes,
- added a comment explaining why the test is only applicable in a certain mode,
- limited the test to language modes where it passes and added a FIXME to fix the checker or the test.
Reviewers: alexfh, lebedev.ri
Subscribers: nemanjai, kbarton, arphaman, jdoerfert, lebedev.ri, cfe-commits
Differential Revision: https://reviews.llvm.org/D62125