While most libraries prefer that readers use their quiet voices, we just visited a library in Copenhagen where talking is actually encouraged.    Ronni Abergel founded The Human Library (or Menneskebiblioteket ) 26 years ago. To be clear, there are no physical books there; the people are called books. "It's a library where we give out human beings on loan, and they'll be an open book for you and answer any question you have about the topic that they're offering," he said. All the "books" are