[cmake] remove DS_OVERRIDE and DS_FINAL

Drop support for override and final keyword discovery since all supported
compiler understand those by now. Further use of DS_OVERRIDE or DS_FINAL
will trigger a compile error.
replaced DS_OVERRIDE and DS_FINAL by override and final, respectively
[test.common_fixed_map] remove wrong DUNE_UNUSED
[test.common_timedlogging] do not use man.hxx

Since the timed logger is by now instantiated in main.hxx to be used in
other tests this test must not use main.hxx but have its own main.