Update offsets before finding where to insert the new value.

Update offsets before finding where to insert the new value.

	* gtk/gtktreemodelsort.c: (gtk_tree_model_sort_insert_value):
	Update offsets before finding where to insert the new value.

	* gtk/gtktreeview.c: (validate_visible_area): Make sure we redraw when
	we scroll, instead of just updating the scroll position variables.