John Hopewell Chief International CorrespondentAidan Gillen, star of “The Wire” and Petyr “Littlefinger” Baelish in “Game of Thrones,” is attached to play one of the leads in “The O’Neill,” a Gaelic Ireland epic turning on its greatest hero, Hugh O’Neill.Stephen Saint Leger, director of “Vikings,” “Vikings: Valhalla” and the climactic “The Battle” episode of “Barbarians,” is also on board, set to helm the series’ pilot and a number of episodes.Set up at Dublin’s Revolution Media, headed by Jack