If you think man-crack is the apex of hilarity, “A Walk in the Woods” just might be the movie for you. It’s all right there in the trailers: slapstick, womp-womp one-liners, the premise of old buddies going on an adventure. See some moon or your money back! So it’s surprising when the opening minutes show promise, thanks to an incredibly preserved Robert Redford, who plays accomplished travel writer Bill Bryson. Even more of a surprise is learning that this film is based on a memoir.