Turns events into vars instead of a list, to greatly simplify qdel() cleanup.

code/datums/observation/observation.dm

@@ -0,0 +1,56 @@
+/datum/observ
+	var/list/listeners
+
+/datum/observ/Destroy()
+	if(listeners)
+		for(var/listener in listeners)
+			unregister(listener)
+		listeners.Cut()
+	return ..()
+
+/datum/observ/proc/register(var/datum/procOwner, var/proc_call)
+	if(!listeners)
+		listeners = list()
+	listeners[procOwner] = proc_call
+	procOwner.destruction.register(src, /datum/observ/proc/unregister)
+
+/datum/observ/proc/unregister(var/datum/procOwner)
+	if(!listeners)
+		return
+	listeners -= procOwner
+	procOwner.destruction.unregister(src)
+
+/datum/observ/proc/raise_event(var/list/args = list())
+	if(!listeners)
+		return
+	for(var/listener in listeners)
+		call(listener, listeners[listener])	(arglist(args))
+
+/***********************
+* Destruction Handling *
+***********************/
+/datum
+	var/datum/observ/destruction
+
+/datum/New()
+	init_observers()
+	..()
+
+/datum/Destroy()
+	destruction.raise_event(list(src))
+	destroy_observers()
+	return ..()
+
+/datum/proc/init_observers()
+	destruction = new()
+
+/datum/proc/destroy_observers()
+	qdel(destruction)
+	destruction = null
+
+// This ensures that observer handlers don't create their own observer handlers, which create their own handlers, which create...
+/datum/observ/init_observers()
+	return
+
+/datum/observ/destroy_observers()
+	return