add a setting to enable a brief lockout after unpausing the game

[ceejbot]

If somebody is using a controller, with a lot of buttons doing double and triple duty, the back button to get out of a paused menu might also be in use as a Soulsy key. This can lead to inadvertent HUD actions while you're still transitioning out of pause.

I think there's no universal de-bouncing here? Anyway, a brief lockout would work.