[v0.20] [proof-of-concept] allow toplevel capture

[Consolatis]

Just to experiment.

Missing:

• [ ] xwayland child windows
• [ ] xwayland unmanaged windows, e.g. popups / menus / ...
• [ ] xdg child window positioning
• [ ] xdg subsurfaces (test-case: mate-terminal settings listboxes)
• [ ] xdg popup positioning

[kode54]

subsurfaces will likely play hell with Firefox in Wayland Webrender mode, since that uses a huge mess of tiled subsurfaces. Which aren't sized and positioned correctly when scale is not equal to 1.0. Eugh.

[kode54]

No longer applies cleanly.

[Consolatis]

No longer applies cleanly.

Thanks, rebased.

[kode54]

This once again needs to be rebased.

[kode54]

This needs a rebase again.