Make exhaustive use of C++11 override keyword (NFC)
It is common practice to mark methods with the
override keyword if they override a base class method. Being pedantic about it can greatly improve the traceability of a code base for the human reader.
Applied clang-tidy modernize-use-override globally in order to achieve compliance in current code base.
suggest-override for CMake target
framaCIRGen in order to detect future breaches.