SDL2 Adds Wayland HiDPI Support

The ever important Simple DirectMedia Layer (SDL) can now handle HiDPI window scaling under Wayland.

Thanks to developer Sebastian Krzyszkowiak, HiDPI support is now in place for SDL2 on Wayland. This code supports drawing the window based upon a scaling factor.

The code is in place for the next release, likely SDL 2.0.10. There's also been a number of CVE security fixes hitting SDL this week around buffer overwrites/overreads, so perhaps the next SDL update won't be taking too long to materialize.