Fixed bug 4986 (Open in <n> new windows disabled)

	* src/file-manager/fm-directory-view.c: (real_update_menus):
	An == should have been a !=

	Fixed bug 3510 (The Back and Forward right-click menus are
	missing)

	* src/nautilus-shell-ui.xml: Replaced toolitem nodes for
	"Back" and "Forward" with control nodes for their wrappers.
	Have to do a lot of stuff manually for non-standard Bonobo
	buttons.

	* src/nautilus-window-private.h: Store back_button_item and
	forward_button_item in details.

	* src/nautilus-window-toolbars.c:
	Removed #ifdef UIH brackets around right-click menu code.
	(get_back_button), (get_forward_button): Helper functions to
	get the GtkButton widgets from the stored BonoboUIToolbarButtonItems.
	(back_or_forward_button_pressed_callback): Renamed from ..._clicked_...,
	since it's a handler for button_press_event. Compare for Back or
	Forward button a newfangled way.
	(back_or_forward_button_clicked_callback): New function, callback
	from button's "clicked" handler now that Bonobo doesn't handle this
	for us.
	(get_file_name_from_icon_name): New function extracted from
	set_up_button; gets the full file path from the leaf icon "name".
	(set_up_standard_bonobo_button): Renamed from "set_up_button",
	now calls get_file_name_from_icon_name.
	(get_pixbuf_for_xml_node): New function, calls Bonobo utility code
	to get the pixbuf from an xml button node.
	(set_up_special_bonobo_button): New function, parallel to
	set_up_standard_bonobo_button but handles the case where you have
	a BonoboUIToolbarButtonItem in hand.
	(set_up_toolbar_images): Call set_up_special_bonobo_button for the
	Back and Forward items; put the bonobo freeze/thaw here instead of
	where it was before in set_up_button.
	(set_widget_for_bonobo_control): New function, extracted from
	nautilus_window_initialize_toolbars, handles attaching a widget to
	a Bonobo control defined in the XML file.
	(set_up_back_or_forward_tool_bar_item): New function, creates
	widget, wraps it in control, and wires up signal handlers.
	(nautilus_window_initialize_toolbars): Call set_up_toolbar_images
	only after Back/Forward buttons are created; create Back/Forward
	buttons and use new helper functions.

	* src/nautilus-window.c:
	(nautilus_window_allow_back), (nautilus_window_allow_forward):
	Set sensitivity of Back/Forward buttons explicitly.