for(var/bad_code in world)

Removes a very large amount of world loops.
Adds a macro to painlessly generate a global list, and the needed code to modify the list when an object is made or deleted automatically.
Cleans up some commented out code.

code/modules/hydroponics/seed_controller.dm

@@ -81,7 +81,7 @@ var/global/datum/controller/plants/plant_controller // Set in New().
 
 	// Make sure any seed packets that were mapped in are updated
 	// correctly (since the seed datums did not exist a tick ago).
-	for(var/obj/item/seeds/S in world)
+	for(var/obj/item/seeds/S in all_seed_packs)
 		S.update_seed()
 
 	//Might as well mask the gene types while we're at it.

code/modules/hydroponics/seed_packets.dm

@@ -1,5 +1,7 @@
 var/global/list/plant_seed_sprites = list()
 
+GLOBAL_LIST_BOILERPLATE(all_seed_packs, /obj/item/seeds)
+
 //Seed packet object/procs.
 /obj/item/seeds
 	name = "packet of seeds"