backends/drm: support applying icc profiles with color management
While applications are still restricted to sRGB, this allows working on sRGB content on displays with a wide color gamut, as the whole ICC profile is applied and not just the VCGT.
For the mechanism to set the profile I left colord in place for now; I'll look into changing that as a follow-up task.
cc #11
Edited by Xaver Hugl