Per-Window Flipping In Present With XWayland Support Revised

While the belated X.Org Server 1.20 is onto the release candidate stage, there still are some feature patches expected to land and among them is the per-window flipping support in the Present extension with support wired through for XWayland.

Worked on last summer via GSoC 2017 was this support by Roman Gilg with a goal of reducing tearing in XWayland windowed environments by adding per-window page-flipping support to Present and wiring that up to XWayland so those X11 apps atop Wayland wouldn't be bound to using just one buffer.

Roman today sent out the latest version of these patches for the X Server. The Present flipping is supported in XWayland when in root-less mode and using GLAMOR acceleration.

These latest patches, which will hopefully be merged to X.Org Server Git soon, can for now be found on xorg-devel.