Added mob.set_stat() proc so we can capture mob stat changes.

Also added a canary to detect attempts to set_stat() on ghosts.

code/modules/mob/dead/observer/observer.dm

@@ -94,8 +94,6 @@
 	plane = PLANE_GHOSTS //Why doesn't the var above work...???
 	verbs += /mob/observer/dead/proc/dead_tele
 
-	stat = DEAD
-
 	var/turf/T
 	if(ismob(body))
 		T = get_turf(body)				//Where is the body located?
@@ -149,6 +147,11 @@
 
 /mob/observer/dead/CanPass(atom/movable/mover, turf/target)
 	return TRUE
+
+/mob/observer/dead/set_stat(var/new_stat)
+	if(new_stat != DEAD)
+		CRASH("It is best if observers stay dead, thank you.")
+
 /*
 Transfer_mind is there to check if mob is being deleted/not going to have a body.
 Works together with spawning an observer, noted above.

code/modules/mob/living/carbon/human/life.dm

@@ -1089,9 +1089,9 @@
 
 	return 1
 
-/mob/living/carbon/human/proc/set_stat(var/new_stat)
-	stat = new_stat
-	if(stat)
+/mob/living/carbon/human/set_stat(var/new_stat)
+	. = ..()
+	if(. && stat)
 		update_skin(1)
 
 /mob/living/carbon/human/handle_regular_hud_updates()

code/modules/mob/living/living.dm

@@ -211,7 +211,6 @@ default behaviour is:
 	else
 		health = getMaxHealth() - getOxyLoss() - getToxLoss() - getFireLoss() - getBruteLoss() - getCloneLoss() - halloss
 
-
 //This proc is used for mobs which are affected by pressure to calculate the amount of pressure that actually
 //affects them once clothing is factored in. ~Errorage
 /mob/living/proc/calculate_affecting_pressure(var/pressure)

code/modules/mob/mob.dm

@@ -1016,6 +1016,11 @@ mob/proc/yank_out_object()
 /mob/proc/updateicon()
 	return
 
+// Please always use this proc, never just set the var directly.
+/mob/proc/set_stat(var/new_stat)
+	. = (stat != new_stat)
+	stat = new_stat
+
 /mob/verb/face_direction()
 
 	set name = "Face Direction"