AKA qt_setstringproperty().
This makes some necessary changes to get qt-light working under QT6: • Replace QSound (deprecated) with QSoundEffect • Replace QVariant datatype enums with QMetaTypes’ • Use new constructor for QVariants in propsetters
git-svn-id: https://code.call-cc.org/svn/chicken-eggs/release/5/qt-light@38001 fca3e652-9b03-0410-8d7b-ac86a6ce46c4