In the final installment of our latest chat with Paul Hirsch, editor of “Mission: Impossible” and author of “In a Cutting Room Far, Far Away,” we talk more about his work with Brian De Palma, how Steve Martin would just park illegally since he could afford the ticket, and how his job as a “movie doctor” on “Exorcist III” was true hell. Also, get details on an unproduced (and never discussed) John Hughes project.