Backpacks now play sound when un/equipped

They did this before, but that was due to all storage items playing
sound. Now only applies to backpacks.

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

@@ -19,6 +19,17 @@
 		playsound(src.loc, src.use_sound, 50, 1, -5)
 	..()
 
+/obj/item/weapon/storage/backpack/equipped(var/mob/user, var/slot)
+	if (slot == slot_back && src.use_sound)
+		playsound(src.loc, src.use_sound, 50, 1, -5)
+	..(user, slot)
+
+/obj/item/weapon/storage/backpack/dropped(mob/user as mob)
+	//dont play sound when dropped on the floor
+	if (loc == user && src.use_sound)
+		playsound(src.loc, src.use_sound, 50, 1, -5)
+	..(user)
+
 /*
  * Backpack Types
  */