Macro caper::game_loop

macro_rules! game_loop {
    ( Input => $input:ident,
      Renderer => $renderer:ident,
      CamState => $cam_state:ident,
      RenderItems => $render_items:ident,
      TextItems => $text_items:ident,
      start => $start:block,
      update => $update:block,
      $ui:ident => $ui_update:block) => { ... };
}

quick macro to use in the examples for easily defining all the modules and game loop