Destroy() cleanups in VOREStation code

* Remove remaining hard del()'s in our code.
* Replace deleted() and gcDestroyed with QDELETED macro.
* Fix some strange calls directly to Del() (capital D)
* Make Destroy() return qdel hints.
* Make a few of the Destroy()'s more comprehensive in cleaning up references.
* In edited Destroy() procs, converted to use qdel_null and qdel_null_list macros when possible for pretty code.
* Removed unused variable `sleevecard`

code/modules/multiz/ladder_assembly_vr.dm

@@ -53,7 +53,7 @@
 						"You start to weld \the [src] to the floor.", \
 						"You hear welding")
 					if(do_after(user, 2 SECONDS))
-						if(deleted(src) || !WT.isOn()) return
+						if(QDELETED(src) || !WT.isOn()) return
 						state = CONSTRUCTION_WELDED
 						to_chat(user, "You weld \the [src] to the floor.")
 						try_construct(user)
@@ -66,7 +66,7 @@
 						"You start to cut \the [src] free from the floor.", \
 						"You hear welding")
 					if(do_after(user, 2 SECONDS))
-						if(deleted(src) || !WT.isOn()) return
+						if(QDELETED(src) || !WT.isOn()) return
 						state = CONSTRUCTION_WRENCHED
 						to_chat(user, "You cut \the [src] free from the floor.")
 				else

code/modules/multiz/open_space_controller.dm

@@ -36,7 +36,7 @@
 
 	for(last_object in turfs_to_process_old)
 		var/turf/T = last_object
-		if(T && !T.gcDestroyed)
+		if(!QDELETED(T))
 			update_turf(T)
 		SCHECK
 

code/modules/multiz/pipes.dm

@@ -91,7 +91,7 @@ obj/machinery/atmospherics/pipe/zpipe/Destroy()
 		node1.disconnect(src)
 	if(node2)
 		node2.disconnect(src)
-	..()
+	. = ..()
 
 obj/machinery/atmospherics/pipe/zpipe/pipeline_expansion()
 	return list(node1, node2)