Make GtkIconSource an opaque datatype, and add a bunch of accessor

Make GtkIconSource an opaque datatype, and add a bunch of accessor

2001-03-19  Havoc Pennington  <hp@redhat.com>

	* gtk/gtkiconfactory.c: Make GtkIconSource an opaque datatype, and
	add a bunch of accessor functions. This is because we have
	reasonable expectations of extending what fields it contains in
	the future.

	* gtk/gtkstyle.c (gtk_default_render_icon): adapt to icon source
	changes

	* gtk/gtkrc.c (gtk_rc_parse_icon_source): fix to use new
	GtkIconSource