This is a combined patch correcting several shortcomings in preliminary support for AMS and including an experimental support for the direct scanout of Wayland buffers for fullscreen windows bypassing the compositor.
**AMS:**
* Test mode for atomic commits
* Cleaned up property adding
* Fixed atomic DPMS
* Other minor fixes regarding potential buffer leaks
* First draft for assigning buffers for overlay planes
**Direct Buffer Scanout:**
* Added new DrmBuffer class (will also be used for overlay planes later)
* Works only on Gl at the moment, skips context switch, uses WindowPixmaps for now.
**Problems / open questions:**
Marked by `TODO_X` and there is still tearing on direct buffer scanout.