* libnautilus-extensions/nautilus-string.c:
	* libnautilus-extensions/nautilus-string.h:
	After a chat with Rebecca, named nautilus_str_underscore_escape to
	nautilus_str_double_underscores since the latter name more
	accurately describes what it does.
	(nautilus_str_double_underscores): Changed the function to allow
	NULL and return NULL instead of doing g_return_val_if_fail.
	(Also reformatted a bit and made a few gratuitous changes.)

	* libnautilus-extensions/nautilus-bookmark.c:
	* libnautilus-extensions/nautilus-bookmark.h:
	(nautilus_bookmark_get_menu_display_name):
	Moved the logic about escaping menu characters up one level so
	the bookmark class doesn't have to know about it. This removes
	the function from NautilusBookmark completely.

	* src/nautilus-window-menus.c:
	(append_bookmark_to_menu): Fixed a storage leak and moved the
	double-underscore escaping in here.