Fixes a display bug seenby ajacoutot@, ok jsg@ and kettenis@. newer X.Org (2.99.917 or master) version cause corruption on older machines (X40, i965), probably caused by a bug in our kernel, under investigation by kettenis@.
Tested by jsg@, kettenis@ and myself on a wide range of intel cards.
A recent kernel with kernel modesetting support is required. Thanks to jsg@ and kettenis@ for their work.