Ran into weird bug in one of RubyGame's dependencies

https://github.com/rubygame/rubygame/issues/21

The fix that solved it (linked from the aforementioned issue):
https://github.com/xrs1133/ruby-sdl-ffi/commit/0b721ac4659b4c08cda5aa2f418561a8a311e85b

More to do, of course.