- fixed: The Hexen bridge must make its balls disappear when it gets destroyed.

Hexen did this with a call to A_BridgeRemove in Thing_Destroy which merely set a flag in the bridge object, which cannot be done safely in ZDoom because it's not guaranteed that the ball object calls A_BridgeOrbit and the garbage collector may delete the bridge actor before it can be checked so now the Bridge's Destroy method deletes all balls attached to the bridge object itself.