Limit recalculations.

Setting based - limit area recalculation and allow tuning of the
interval.

hud.lua

@@ -1,8 +1,17 @@
 -- This is inspired by the landrush mod by Bremaweb
 
 areas.hud = {}
+areas.hud.refresh = 0
 
 minetest.register_globalstep(function(dtime)
+
+	areas.hud.refresh = areas.hud.refresh + dtime
+	if areas.hud.refresh > areas.config["tick"] then
+		areas.hud.refresh = 0
+	else
+		return
+	end
+
 	for _, player in pairs(minetest.get_connected_players()) do
 		local name = player:get_player_name()
 		local pos = vector.round(player:getpos())