* docs/reference/libxfce4menu-sections.txt,

	  libxfce4menu/xfce-menu-directory.{c,h},
	  libxfce4menu/xfce-menu-element.{c,h},
	  libxfce4menu/xfce-menu-item.{c,h},
	  libxfce4menu/xfce-menu-separator.c,
	  libxfce4menu/xfce-menu.c: Add xfce_menu_element_get_no_display() and
	  xfce_menu_element_get_visible_in_environment() to the
	  XfceMenuElement interface. Implement this in XfceMenu,
	  XfceMenuDirectory, XfceMenuItem and XfceMenuSeparator.