Some keypresses fail to register immediately

[outfrost]

When multiple keys are pressed simultaneously (probably within the same iteration of the main loop), GLFW gives us a callback for only one of those keys. Further keys might be accounted for when repeat kicks in.

For example, when we press W and D at once, one of them (e.g. W) will be picked up instantly, and the other (e.g. D) will be 'seen' after a brief delay.

Even more bizarre issues come up when trying to press 3 or 4 movement keys in the same instant.