immediate update of scroll area). Some related bugs
	remain, which I'll write up separately

	* libnautilus-extensions/nautilus-gnome-extensions.h:
	* libnautilus-extensions/nautilus-gnome-extensions.c:
	(nautilus_gnome_canvas_set_scroll_region_include_visible_area):
	New function, sets scroll region to given parameters,
	also forcing visible area to be included.

	* libnautilus-extensions/nautilus-icon-container.c:
	(update_scroll_region): New function, extracted from
	nautilus_icon_container_update_scroll_region, now takes
	boolean for whether to include the visible area.
	(nautilus_icon_container_update_scroll_region): Now calls
	update_scroll_region.
	(nautilus_icon_container_update_scroll_region_include_visible_area):
	New function, calls update_scroll_region.
	(size_allocate): Do no work if allocation hasn't changed. This
	didn't help with bug 2068 but is a worthwhile optimization.

	* libnautilus-extensions/nautilus-icon-private.h:
	Prototype for nautilus_icon_container_update_scroll_region_
	include_visible_area

	* libnautilus-extensions/nautilus-icon-dnd.c: (handle_local_move):
	call ..._include_visible_area when updating scroll region after
	drag & drop, instead of just ..._update_scroll_region, so no
	origin-shifting occurs.