Paul de Barros Back in the early ???60s, when every musician I knew, including me, was trying to learn guitar so we could play folk songs like Bob Dylan or blues like Lightnin??? Hopkins, one of the guys we all copied was Dave Van Ronk, the bearded finger-picker with the brawny, salt???n???pepper voice whose life story has now inspired the Coen Brothers??? poignant new film about the early-???60s