You must remember this, because the story of how “Casablanca” came to be is one of Hollywood’s most oft-told tales. Legends of daily script rewrites and actors standing around on set waiting to find out whether or not Bogie was gonna get on that plane with Ingrid Bergman have filled dozens of retrospective television specials, DVD extras and countless books about the troubled shoot. (I’ve got at least two in the other room.) Those who already know that Ronald Reagan and Ann Sheridan were originally announced as Rick and Ilsa might wonder if yet another book about the making of this American classic could possibly offer anything new, but Leslie Epstein’s “Hill of Beans: A Novel of War and Celluloid” is hardly the same old story. It’s a blisteringly funny, fictional farce using the film’s famous production woes as the backdrop for a bawdy espionage adventure boasting an all-star cast of world leaders and movie industry icons, with the fate of the free world hanging in the balance.