Bug fixes.

	5776 - Preferences dialog layout updates incorrectly after
	switching user level.

	5791 - Preference section title are visible even when section is
	empty.

	* libnautilus-extensions/nautilus-preferences-box.h:
	* libnautilus-extensions/nautilus-preferences-box.c:
	(nautilus_preferences_box_initialize_class),
	(nautilus_preferences_box_initialize),
	(nautilus_preferences_box_destroy), (preferences_box_select_pane),
	(preferences_box_category_list_recreate), (pane_info_new),
	(pane_info_free), (category_list_select_row_callback),
	(nautilus_preferences_box_new),
	(nautilus_preferences_box_add_pane),
	(nautilus_preferences_box_update):
	Lots of cleanup.  Fix typos in many class macros and methods.
	Comply with the Nautilus style more.  Remove unused code.

	Recreate the category list whenever the preference box gets
	updated in order to honor user level visibilities.

	* libnautilus-extensions/nautilus-preferences-dialog.h:
	* libnautilus-extensions...