demo: fixed on windows

demo/CheckBox/DemoCheckBox.pas

@@ -5,7 +5,11 @@ unit DemoCheckBox;
 interface
 
 uses
-  Classes, SysUtils, FPReadPNG, Fresnel.DOM, Fresnel.Controls, Fresnel.Classes,
+  Classes, SysUtils,
+  {$IFDEF Windows}
+  Windows,
+  {$ENDIF}
+  FPReadPNG, Fresnel.DOM, Fresnel.Controls, Fresnel.Classes,
   FCL.Events, Fresnel.Events;
 
 type