makes w_class use defines (#9848)

code/game/objects/items/weapons/tanks/jetpack.dm

@@ -36,7 +36,7 @@
 	icon_state = "jetpack"
 	item_state = "jetpack"
 	gauge_icon = null
-	w_class = 4.0
+	w_class = ITEMSIZE_LARGE
 	distribute_pressure = ONE_ATMOSPHERE*O2STANDARD
 	var/datum/effect_system/ion_trail/ion_trail
 	var/on = 0.0

code/game/objects/items/weapons/tanks/tank_types.dm

@@ -114,7 +114,7 @@
 	gauge_cap = 4
 	flags = CONDUCT
 	slot_flags = SLOT_BELT
-	w_class = 2.0
+	w_class = ITEMSIZE_SMALL
 	force = 4.0
 	distribute_pressure = ONE_ATMOSPHERE*O2STANDARD
 	volume = 2 //Tiny. Real life equivalents only have 21 breaths of oxygen in them. They're EMERGENCY tanks anyway -errorage (dangercon 2011)
@@ -151,7 +151,7 @@
 	gauge_cap = 4
 	flags = CONDUCT
 	slot_flags = SLOT_BELT
-	w_class = 2.0
+	w_class = ITEMSIZE_SMALL
 	force = 4.0
 	distribute_pressure = ONE_ATMOSPHERE*O2STANDARD
 	volume = 2

code/game/objects/items/weapons/tanks/tanks.dm

@@ -18,7 +18,7 @@
 
 	flags = CONDUCT
 	slot_flags = SLOT_BACK
-	w_class = 3
+	w_class = ITEMSIZE_NORMAL
 
 	force = 5.0
 	throwforce = 10.0
@@ -309,4 +309,4 @@
 
 /obj/item/tank/proc/remove_air_by_flag(flag, amount)
 	. = air_contents.remove_by_flag(flag, amount)
-	update_icon()
+	update_icon()

code/game/objects/items/weapons/tanks/watertank.dm

@@ -5,7 +5,7 @@
 	icon_state = "waterpack"
 	item_state = "waterpack"
 	contained_sprite = 1
-	w_class = 3
+	w_class = ITEMSIZE_NORMAL
 	slot_flags = SLOT_BACK
 
 	var/obj/item/reagent_containers/spray/chemsprayer/mister/noz
@@ -95,7 +95,7 @@
 	icon_state = "mister"
 	item_state = "mister"
 	contained_sprite = 1
-	w_class = 3
+	w_class = ITEMSIZE_NORMAL
 	amount_per_transfer_from_this = 50
 	volume = 500
 	slot_flags = 0