[FEATURE] Safety airlocks.

[Erik]

If the airlock is shocked and the safety wire is cut, it should shock whoever it closes on.

This would be possible, but the current door_parent and airlock code is such as mess that I'd rather finish my parallax patch first before rewriting the entire airlock, wire and door systems. I merely did this change between the two patches as it was an interesting idea that could easily be implemented without making too much changes.