In two weeks, Minneapolis voters will decide whether to approve $110-million dollars for a new Central Library. The current building, located between Hennepin and Nicollet Avenues, was built in 1961 and is already packed with more than two and a half million books, magazines tapes and videos, most of which are locked away from the public, accessible only through a librarian. Last week the library began offering tours of its extensive "stacks" collection to let the public see some of its hidden treasures. Officials say the hour-and-a-half tours are not linked to the upcoming vote for a new library.