Oliver Stone and the studio releasing his $150 million historical epic "Alexander" should beware of Greeks bearing writs — over the film's depiction of Alexander the Great as Alexander the Fabulous. The controversial director and Warner Bros. were yesterday threatened with a lawsuit by a group of Greek lawyers who are incensed that the new movie "Alexander" portrays the hero as bisexual. The group of 25 Athens-based lawyers said they sent a letter to Warner Bros. demanding that it label "Alexander" ... as a work of fiction.... "We are not saying that were are against gays, but we are saying...