Photo by Joan MarcusShe can climb ev'ry mountain, but she can't tap-danceIt's been years since Roy Hamlin, associate artistic director at Theatre Under the Stars, has had anything to do with The Sound of Music -- not since his high school days when he was playing Uncle Max.Now he gets to direct it professionally, to do the one-more-time thing at Hobby Center this December. And, he insists, that people who think there's nothing there for them but chestnuts with hair growing on them, should thi