Mouse Skeletons (#1279)

Adds decomposing animations for mice when dusted. They'll leave behind a little mouse skeleton
Mice and lizards will decompose to a skeleton 30 mins after death, or if dusted

Also some fixes to various small issues and runtime errors related to held mobs and supermatters.

code/modules/mob/death.dm

@@ -25,8 +25,11 @@
 //This is the proc for turning a mob into ash. Mostly a copy of gib code (above).
 //Originally created for wizard disintegrate. I've removed the virus code since it's irrelevant here.
 //Dusting robots does not eject the MMI, so it's a bit more powerful than gib() /N
-/mob/proc/dust(anim="dust-m",remains=/obj/effect/decal/cleanable/ash)
+/mob/proc/dust(anim="dust-m",remains=/obj/effect/decal/cleanable/ash, iconfile = 'icons/mob/mob.dmi')
 	death(1)
+	if (istype(loc, /obj/item/weapon/holder))
+		var/obj/item/weapon/holder/H = loc
+		H.release_mob()
 	var/atom/movable/overlay/animation = null
 	transforming = 1
 	canmove = 0
@@ -35,7 +38,7 @@
 
 	animation = new(loc)
 	animation.icon_state = "blank"
-	animation.icon = 'icons/mob/mob.dmi'
+	animation.icon = iconfile
 	animation.master = src
 
 	flick(anim, animation)