Change end-of-game advantage calculator to use [unit_worth].

data/multiplayer/eras.cfg

@@ -78,7 +78,10 @@
                     -- Calc the total unit-score here
                     for i, unit in ipairs( wesnoth.get_units { side = side } ) do
                         if not unit.__cfg.canrecruit then
-                            units = units + unit.__cfg.cost
+                            wesnoth.fire("unit_worth",{
+                                id = unit.__cfg.id,
+                            })
+                            units = units + wesnoth.get_variable("unit_worth")
                         end
                     end
                     -- Up to here