some translatable strings show untranslated

See the lupdate warning of the MacOS_lupdate job on Travis CI, for example https://travis-ci.org/musescore/MuseScore/jobs/521621017#L109-L112:

/Users/travis/build/musescore/MuseScore/libmscore/durationtype.cpp:794: Qualifying with unknown namespace/class ::TDuration
/Users/travis/build/musescore/MuseScore/mscore/musicxmlsupport.cpp:175: Class 'Ms::ValidatorMessageHandler' lacks Q_OBJECT macro
/Users/travis/build/musescore/MuseScore/mscore/plugin/mscorePlugins.cpp:419: Qualifying with unknown namespace/class ::MuseScore
/Users/travis/build/musescore/MuseScore/mscore/preferenceslistwidget.cpp:30: Class 'Ms::PreferencesListWidget' lacks Q_OBJECT macro

1. the 17 strings from libmscore/durationtype.cpp, lines 794-811 show in Transifex, not sure they would show translated in MuseScore, not excactly sure where they should show. I believe they show in the status bar when a note or rest or a tempo text is selected, and if so, they do show translated, so the lupdate warning/error might just be wrong. Also ISTR to have that particular one since ages.
2. the 6 strings from mscore/musicxmlsupport.cpp, lines 175-182 show in Transifex, but don't show translated in MuseScore. The lupdate warning/error is the same as for the last one, and there the string does not show translated, we seem to have an issue here too, Translations for them got added in PR #4492, as part of work at #281133: [MusicXML] Score exported to XML doesn't import back cleanly and the string indeed do still show intranslated.
3. the 3 strings from mscore/plugin/mscorePlugins.cpp, lines 419-421 show in Transifex, and show translated in MuseScore. The lupdate warning/error is similar to the first and that doesn't seem to be an issue, this here apparently isn't either.
4. the 4 strings from mscore/preferenceslistwidget.cpp, lines 30-34, do show up on Transifex, but at least "Preference" and "Value" don't show translated in Edit > Settings... > Advanced

So those 2 Class '...' lacks Q_OBJECT macro messages seems to point at real issues, and are probably easy to fix .
The other 2 are basically just an annoyance, but seem to do no harm.