Made get/set_swap_interval take and return an enum instead of i32
Made get/set_swap_interval take and return an enum instead of i32

Cobrand/rust-sdl2,Cobrand/rust-sdl2,Rust-SDL2/rust-sdl2,Rust-SDL2/rust-sdl2,AngryLawyer/rust-sdl2,Rust-SDL2/rust-sdl2,Cobrand/rust-sdl2