If you’ve read William Friedkin’s 500-page autobiography, “The Friedkin Connection,” or the interviews he has done with The Criterion Collection, you know the veteran filmmaker is a raconteur of the highest order. Many of those tales are repeated in the new documentary, “Leap of Faith,” a reverential look at the 85-year-old director’s classic, still-chilling, career-making horror, “The Exorcist.”