[Announcement] Qt6 Support by removing deprecated functions

Created by: basyskom-dege

Since Qt6 was released recently, it would be a good to support that. The existing Qt5 generator uses some deprecated functions that are not supported in Qt6. I replaced them with the equivalent Qt6 functions. The new functions work with Qt5 aswell, except of the Qt::SectionSkipEmpty Flag ( equal to 0x01) that was in the QString namespace in Qt5. I inserted a preprocessor variable to support both, Qt5 and Qt6:

#if QT_VERSION >= 0x060000
    #define SKIP_EMPTY_PARTS Qt::SkipEmptyParts
#else
    #define SKIP_EMPTY_PARTS QString::SkipEmptyParts
#endif

I created a PR with those changes. Since the generator is called cpp-qt5-generator it would make sense to add a new Qt6 generator or rename it.