RFC: patch to support fullscreen shell wayland compositors

Hello all,

I created a patch for SDL2 to allow SDL applications to run inside a fullscreen shell wayland compositor. Basically, the goal of fullscreen shell is to nest another wayland compositor underneath it (for providing things like fast shell switching), but another use is for single applications having complete control over the screen without needing to implement all the DRM logic.

I made a post on the bugzilla with the patch (https://bugzilla.libsdl.org/show_bug.cgi?id=3630) and a description of what it does, but I’ve seen other patches get posted to the mailing list so I figured I’d send it here too.