problem with openlayers on screens with h DPI (probably)

On MAC OS when showing the map on retina screens in Safari and Chrome there is a problem with scaling of the map...

originally reported by @nils.christian

created branch 421-problem-with-openlayers-on-screens-with-h-dpi-probably

mentioned in merge request !312 (merged)

closed via merge request !312 (merged)

mentioned in commit c282a00a

It's a problem with openlayers library: https://github.com/openlayers/openlayers/issues/8253