Cross-cutting event bits for trap door and task state.

Bit	Meaning
00	Room / script event raised (set by helpers such as Script_Shared_SetEventBit)
01	Trap door is open / trap door event armed
02	Falling-entity latch (cleared/set by Process_Falling_Entities)
03	Object has been offered to the trap (Bad Tempered Thing path)
04	Task-two / upstairs event latch
05	Reserved / unused in the observed call sites
06	Special put-down / room-transition event
07	Task entity script is active