"Couldn't find any available vsync extension" even if I set vsync to false

[ProgrammingLife]

When I run simple example with vsync set to false I get:

libEGL warning: DRI2: failed to authenticate
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: CreationErrors([NoAvailablePixelFormat, OsError("Couldn't find any available vsync extension")])', src/main.rs:8:36
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Is this possible to run app without checking for vsync extension? My system doesn't have one and I'm going to work with my app in headless mode.

[kchibisov]

Fixed in #1435.