HOLDENVILLE, Okla. – They were once unwanted, abandoned and on the verge of being euthanized. But earlier this month nearly a dozen shelter dogs graduated from a unique training program behind the wire of Allen Gamble Correctional Center.The program, known as “Pen Pals,” is celebrating its 20th anniversary this year.“We are a win-win situation,” said Jonathon Cox with Pauls Valley-based Buckaroos…