Hollywood -- Roddy McDowall, who portrays a chimpanzee friendly to two astronauts in the year 3085 A.D. in “Planet of the Apes,” is recognised as one of the most proficient professional photographers in Hollywood.   His photographic layouts have appeared in leading magazines throughout the United States and Europe, and he has been a contributing editor for Harper’s Bazaar. He also published a successful photo-illustrated book, “Double Exposure.”   McDowall took up his second career seriously in 1953, when he was appearing in “Misalliance,” and he has been firing away ever since.   “But when death came to so many fine magazines like Life and Look,” said McDowall, “the market became ridiculously small and I’m no longer as active as I was in the field.”