Make demo work with newest sdl2 and rust nightly.
Make demo work with newest sdl2 and rust nightly.

Rust-SDL2/rust-sdl2,vadixidav/rust-sdl2,Rust-SDL2/rust-sdl2,AngryLawyer/rust-sdl2,andelf/rust-sdl2_gfx,Cobrand/rust-sdl2,Cobrand/rust-sdl2,Cobrand/rust-sdl2,Rust-SDL2/rust-sdl2