[Development] shadowing properties (and methods)

[Ulf Hermann]

> We also have the Q_OVERRIDE macro. It is used extensively by QTextBrowser to override 3 properties, and…. nowhere else in Qt. Github knows of one more exact match in KDE/kommander.

I kind of want to use Q_VIRTUAL, Q_OVERRIDE and Q_FINAL as replacements 
for Q_INVOKABLE to mark functions that can(not) be overridden or are 
overriding something. The QTextBrowser special case would have to be 
migrated to some other mechanism then.

This is controversial, of course. I'd be grateful for some suggestions 
on how to deal with shadowing of invokables. So far, the discussion 
hasn't progressed very far.

best regards,
Ulf Hermann