multimedia/mkvtoolnix: Update to upstream release 60.0.0
Details:
- Major features, bug fixes and build system changes in 59.0.0 and 60.0.0, see https://mkvtoolnix.download/doc/NEWS.md , a.o:
- QT5 is now required for the non-gui version as well, subsequently the QT5 OPTION has been renamed to GUI.
- Since QT5 support on FreeBSD 11 is limited, this will no longer build on FreeBSD 11 and is marked BROKEN.