Layers are now defines (#17949)

* Layers are now defines

* this looks better

* GAS_phil_LAYER

* no message

* remove the three unneeded defines

* no message

code/game/objects/items/documents.dm

@@ -8,7 +8,7 @@
 	w_class = 1
 	throw_range = 1
 	throw_speed = 1
-	layer = 4
+	layer = MOB_LAYER
 	pressure_resistance = 1
 
 /obj/item/documents/nanotrasen

code/game/objects/items/stacks/sheets/leather.dm

@@ -155,7 +155,7 @@ var/global/list/datum/stack_recipe/sinew_recipes = list ( \
 	singular_name = "hide plate"
 	flags = NOBLUDGEON
 	w_class = 3
-	layer = 4
+	layer = MOB_LAYER
 
 /obj/item/stack/sheet/animalhide/ashdrake
 	name = "ash drake hide"
@@ -165,7 +165,7 @@ var/global/list/datum/stack_recipe/sinew_recipes = list ( \
 	singular_name = "drake plate"
 	flags = NOBLUDGEON
 	w_class = 3
-	layer = 4
+	layer = MOB_LAYER
 
 
 //Step one - dehairing.

code/game/objects/items/stacks/sheets/mineral.dm

@@ -63,7 +63,7 @@ var/global/list/datum/stack_recipe/sandstone_recipes = list ( \
 	icon_state = "sandbags"
 	singular_name = "sandbag"
 	force = 5
-	layer = 2.95
+	layer = LOW_ITEM_LAYER
 	throwforce = 5
 	w_class = 3
 	throw_speed = 1

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

@@ -157,7 +157,7 @@
 	boxes.screen_loc = "[tx]:,[ty] to [mx],[my]"
 	for(var/obj/O in contents)
 		O.screen_loc = "[cx],[cy]"
-		O.layer = 20
+		O.layer = ABOVE_HUD_LAYER
 		cx++
 		if(cx > mx)
 			cx = tx
@@ -176,7 +176,7 @@
 			ND.sample_object.mouse_opacity = 2
 			ND.sample_object.screen_loc = "[cx]:16,[cy]:16"
 			ND.sample_object.maptext = "<font color='white'>[(ND.number > 1)? "[ND.number]" : ""]</font>"
-			ND.sample_object.layer = 20
+			ND.sample_object.layer = ABOVE_HUD_LAYER
 			cx++
 			if(cx > (4+cols))
 				cx = 4
@@ -186,7 +186,7 @@
 			O.mouse_opacity = 2 //This is here so storage items that spawn with contents correctly have the "click around item to equip"
 			O.screen_loc = "[cx]:16,[cy]:16"
 			O.maptext = ""
-			O.layer = 20
+			O.layer = ABOVE_HUD_LAYER
 			cx++
 			if(cx > (4+cols))
 				cx = 4
@@ -464,11 +464,11 @@
 	boxes.master = src
 	boxes.icon_state = "block"
 	boxes.screen_loc = "7,7 to 10,8"
-	boxes.layer = 19
+	boxes.layer = HUD_LAYER
 	closer = new /obj/screen/close()
 	closer.master = src
 	closer.icon_state = "backpack_close"
-	closer.layer = 20
+	closer.layer = ABOVE_HUD_LAYER
 	orient2hud()