hidpi + qt 5.6

[Harald Sitter]

Hellowsies,

Please note that you want to rebuild kwin (and probably workspace and
desktop for good measure) to ensure hidpi is working properly with Qt
5.6 (there are some ifdefs there).

otherwise things will be off
https://bugs.kde.org/show_bug.cgi?id=362767

This is of course in addition to private-ABI-usage rebuilds that might
be needed. kdeclarative, plasma-framework, frameworkintegration and
plasma-integration are usually good candidates for that.

HS