Merge sw cursor support for DisplayLink displays to xserver1.20 branch
The miPointerSpriteFunc swcursor code expects there to only be a single framebuffer and when the cursor moves it will undo the damage of the previous draw, potentially overwriting what ever is there in a new framebuffer installed after a flip.
This leads to all kind of artifacts, so we need to disable pageflipping when a swcursor is used.
The code for this has shamelessly been copied from the xf86-video-amdgpu code.
Fixes: #828 (closed)