make sure we're surpressing ALL later handling of hotkeys, not just menu handling

[ceejbot]

The use case here is somebody wanting to bind shift-left-click to a HUD action, while not triggering the main game context left-click behavior. I suspect if I do this, I'm going to have to switch to acting on key-down instead of key-up, which is something I'm going to have to test carefully. It's a lot of long-standing code in the trickiest paths. OTOH, a third rewrite of that stuff will probably improve on the current implementation.

Take the approach here in the menu handler and apply it here in the gameplay key event handler when we know we did something with it. Also review the Rust-side handler logic to be sure it's returning the right thing every time, because until we make this change we won't have been relying on that being correct.

[ceejbot]

This is probably fixed, but I need to find a way to test it.