support haiku and cygwin

[SArpnt]

i don't think either of these platforms have much progress on a wayland compositor yet, but as far as i can tell nothing is preventing a wayland compositor from working on these platforms.

currently wayland-backend doesn't build because there isn't a polling implementation, epoll and kqueue are picked for other platforms based on feature flags. not sure if there's any other issues.

the details involved here are well outside my knowledge but i am working on a wayland application and it would be nice to support all major platforms without linux vms. i might try to work on this myself when i'm less busy.

[ids1024]

I don't think Windows (or cygwin) have a way to pass file descriptors over a Unix domain socket? The Wayland protocol isn't really possible to implement without that.

In a quick search, I guess https://github.com/X547/wayland-server is what there is currently for Wayland on Haiku? Not sure how well that works, but it at least has a commit last month.

For reference, libwayland also assumes epoll support. (And uses epoll-shim on BSDs.)