Allow set_opacity() to work for turfs too.

Fixes lighting opacity not updating on mined rock walls and false doors.

code/modules/lighting/lighting_atom.dm

@@ -85,7 +85,7 @@
 		return
 
 	opacity = new_opacity
-	var/turf/T = loc
+	var/turf/T = isturf(src) ? src : loc
 	if(!isturf(T))
 		return
 

code/modules/mining/mine_turfs.dm

@@ -82,7 +82,7 @@ var/list/mining_overlay_cache = list()
 /turf/simulated/mineral/proc/update_general()
 	update_icon(1)
 	if(ticker && ticker.current_state == GAME_STATE_PLAYING)
-		// TODO - Look into this
+		recalc_atom_opacity()
 		reconsider_lights()
 		if(air_master)
 			air_master.mark_for_update(src)