GtkToolPalette: Use gtk-toolbar-style and gtk-toolbar-icon-size settings.

GtkToolPalette: Use gtk-toolbar-style and gtk-toolbar-icon-size settings.

	* gtk/gtksettings.c: (settings_install_property_parser): Handle enums too.
	* gtk/gtktoolbar.c (gtk_toolbar_class_init): Move the gtk-toolbar-style and
	gtk-toolbar-icon-size settings into GtkSettings because we now use it in
	GtkToolPalette too.

	* gtk/gtktoolpalette.[h|c]: Add gtk_tool_palette_unset_style() and
	gtk_tool_palette_unset_icon_size(), and use the toolbar-style and
	icon-size from GtkSettings if these are not set via the set functions.

	* demos/gtk-demo/toolpalette.c (on_combo_style_changed),
	(do_toolpalette): Add and handle a -1 value to mean the desktop "Default"
	toolbar style.