The instance_deactivated list is never cleared between rooms.

**EDIT**: Further testing is required; don't merge just yet.

From my tests, the instance_deactivated list is never cleared between rooms. That means deactivated instances can, in some cases, overwrite new (correct) instances after changing rooms. This pull request fixes a few room-related bugs in Iji, all of which involve visiting the same room twice (hence the 

My only concern with this pull request is that I am not 100% clear on the memory management that takes place for instances. In other words: does clearing instance_deactivated create a memory leak?