Qt 5.8.0 incompatible with Plasma/Wayland

[Martin Gräßlin]

Hi distros,

unfortunately Qt 5.8.0 shipped with a regression completely breaking 
Plasma on Wayland: https://bugreports.qt.io/browse/QTBUG-58423

I wanted to let you know, just in case you want to ship out Qt 5.8 and 
Plasma 5.9 and tell your users things like "Hey, test the new Wayland 
stuff".

Personally I would appreciate if Qt 5.8.0 is not combined with Plasma on 
Wayland at all as it makes our work look really, really bad. If you want 
to ship Qt 5.8 that's fine with me, but then make it conflict 
Plasma/Wayland completely, so that no user can run it. The problem is 
present with any version of Plasma, so it's not limited to our new 
Plasma 5.9 release.

Thanks!

Martin