Actor and screenwriter Wentworth Miller, best known for his leading role in “Prison Break,” came out as a gay man on Wednesday in a letter declining an invitation to attend a Russian film festival in light of Moscow’s recently adopted anti-gay laws. Miller, 41, turned down an offer to attend the St. Petersburg International Film Festival as a “guest of honor” in a letter posted on the website of advocacy group GLAAD. “Thank you for your kind invitation. As someone who has enjoyed visiting Russia in the past and can also claim a degree of Russian ancestry, it would make me happy to say yes. However, as a gay man, I must decline,” Miller wrote to the festival director.