Little Holodeck refactor.

code/game/area/areas/holodeck.dm

@@ -6,6 +6,8 @@
 	hidden = TRUE
 
 	var/obj/machinery/computer/holodeck/linked
+	var/list/compatible_holodeck_comps
+	var/abstract_type = /area/holodeck
 	var/restricted = 0 // if true, program goes on emag list
 
 /*
@@ -53,6 +55,8 @@
 */
 /area/holodeck/rec_center
 	name = "\improper Recreational Holodeck"
+	compatible_holodeck_comps = list(/obj/machinery/computer/holodeck)
+	abstract_type = /area/holodeck/rec_center
 
 /area/holodeck/rec_center/offline
 	name = "Holodeck - Offline"