Fixing Airlocks (#1546)

Fixes #1519
Fixes #1531
Fixes #1487
Fixes #1475

Adds a new airlock sprite for freezer-maint airlocks, and assorted periphery

code/game/objects/structures/door_assembly.dm

@@ -83,6 +83,12 @@
 	airlock_type = "/freezer"
 	glass = -1
 
+/obj/structure/door_assembly/door_assembly_fma
+	base_icon_state = "mai"
+	base_name = "Freezer Maintenance Access"
+	airlock_type = "/freezer_maint"
+	glass = -1
+
 /obj/structure/door_assembly/door_assembly_hatch
 	base_icon_state = "hatch"
 	base_name = "Airtight Hatch"

code/game/objects/structures/plasticflaps.dm

@@ -68,6 +68,7 @@
 /obj/structure/plasticflaps/airtight
 	name = "airtight plastic flaps"
 	desc = "Heavy duty, airtight, plastic flaps."
+	layer = 3
 
 /obj/structure/plasticflaps/airtight/New() //set the turf below the flaps to block air
 	var/turf/T = get_turf(loc)