Removed the "extra widget" bit, implemented with the following:

Removed the "extra widget" bit, implemented with the following:

2003-09-03  Federico Mena Quintero  <federico@ximian.com>

	* TODO: Removed the "extra widget" bit, implemented with the
	following:

	* gtkfilechooser.h: Added gtk_file_chooser_{set,get}_extra_widget().

	* gtkfilechooser.c (gtk_file_chooser_base_init): Install an
	"extra-widget" interface property.
	(gtk_file_chooser_set_extra_widget): Implemented.
	(gtk_file_chooser_get_extra_widget): Implemented.

	* gtkfilechooserutils.h (GtkFileChooserProp): Added
	GTK_FILE_CHOOSER_PROP_EXTRA_WIDGET.

	* gtkfilechooserutils.c (_gtk_file_chooser_install_properties):
	Added the "extra-widget" property.

	* gtkfilechooserimpldefault.c (struct _GtkFileChooserImplDefault):
	Added an extra_widget field.
	(gtk_file_chooser_impl_default_set_property): Handle the
	"extra-widget" property.
	(gtk_file_chooser_impl_default_get_property): Likewise.
	(set_preview_widget): Fix the call gtk_container_remove().  Also,
	we don't need to ref/sink/unref the preview widget, as that gets
	already done by container_add/remove.
	(set_extra_widget): New utility function.

	* testfilechooser.c (main): Add an extra widget.