Mac OS: QAction::MenuRole heuristics oddities

The heuristics are bound to fail if there is for example a mismatch
between qApp->appName and the action's text or something is named differently.

Using a translation makes this even more likely (as there might be no translations of
the single words that it checks for). It also is somewhat computationally expensive
as tr("About"...) is done every time.

There also appears to be some fiddling on the actions' text.

This is somewhat unsatisfactory.

At least, it should be clearly documented that the heuristics depend on the language
and that if one is planning to create a Mac App, setting the role explicitly is
strongly recommended.

It is questionable whether the default heuristics role makes sense.