2010-04-22 Andreas J. Guelzow <aguelzow@pyrshep.ca>

	* dialog-sheet-order.c (cb_sheet_order_cnt_visible): simplify
	(sheet_order_cnt_visible): ditto
	(cb_toggled_visible): we are now ensuring that we are the only
	  modifier
	(sheet_selection_can_toggle): new
	(create_sheet_list): hook up sheet_selection_can_toggle