Actor Mike Mitchell, who appeared in "Gladiator" and "Braveheart," has died ... TMZ has learned.Mitchell's rep tells TMZ the actor/bodybuilder died Friday on a boat in Turkey. The family says they believe he suffered a death from natural causes, although they weren't more specific.The rep says, "It was very hard to believe ... The sudden death of an international actor we managed, an honest person, a real actor, a true friend, my dear friend, has saddened us deeply. I've always been honored to be your manager. I wish patience to you wife, dear Denise Mitchell, and your children. Getting to...