This way the hooks have access to what CheckForWin's return value would be if they don't override it (that's why "win" is in hook.Call's varargs).

I was gonna put it inside CheckForWin at first but it doesn't seem to ever be called from anywhere else, and if for some reason you need access to the would-be "win" value from inside the hook, calling CheckForWin inside the hook wouldn't work and would cause an infinite loop.