Fixed bug 2667 (Really long bookmark titles stretch bookmarks menu)

	* libnautilus-extensions/nautilus-gtk-extensions.h:
	* libnautilus-extensions/nautilus-gtk-extensions.c:
	(nautilus_truncate_text_for_menu_item): New function,
	uses nautilus_str_middle_truncate to create a string
	that isn't ridiculously long.

	* libnautilus-extensions/nautilus-bookmark.c:
	(nautilus_bookmark_menu_item_new): Use new function to
	keep the menu items in the Back/Forward context menus
	from getting too wide.
	* src/nautilus-window-menus.c: (append_bookmark_to_menu):
	Use new function to keep the menu items in the Go and
	Bookmarks menus from getting too wide.