Codechange: Store EncodedString for tooltip text.

This replaces capturing and storing string parameters.

src/vehicle_gui.cpp

@@ -2818,7 +2818,7 @@ struct VehicleDetailsWindow : Window {
 			} else {
 				tool_tip = widget == WID_VD_INCREASE_SERVICING_INTERVAL ? STR_VEHICLE_DETAILS_INCREASE_SERVICING_INTERVAL_TOOLTIP_DAYS : STR_VEHICLE_DETAILS_DECREASE_SERVICING_INTERVAL_TOOLTIP_DAYS;
 			}
-			GuiShowTooltips(this, tool_tip, close_cond);
+			GuiShowTooltips(this, GetEncodedString(tool_tip), close_cond);
 			return true;
 		}