HiDPI Support for Okular
This patch enables HiDPI throughout the application
Every pixmap is multiplied by the devicePixelRatioF
QPainter code is ajusted to take the DPR value into account
All pixmaps get cached with the highest DPR of all screens. When moving the application to another screen, the cache doesn't have to be invalidated.
BUGS: 362856 383589