Set world activity state to argument. If 0, remove ./server/worldstate file.
Else, if world was so far inactive, a map exists, at least one "wait" thing
action is defined, and a thing of ID 0 (= a player character) that is not part
of any other thing's inventory, (re-)build all animate things' fields of view,
and activate world. (Initial value: 0.)
Set world activity state to argument. If 0, remove ./server/worldstate file.
Else, if world was so far inactive, a map exists, at least one "wait" thing
action is defined, and a thing of ID 0 (= a player character) that is not part
of any other thing's inventory, (re-)build all animate things' fields of view,
and activate world. (Initial value: 0.)