You may be wondering: Can a shirtless guy in his mid-50s who dresses in purple velour shorts still rock like he did in 1979? I know I asked myself the same question before AC/DC took the stage Wednesday night at U.S. Airways Center. But now I'm done doubting my aging heroes. Like other dinosaurs I've seen in the past decade or so -- Pete Townshend, Johnny Cash, Nick Lowe, Deniz Tek of Radio Birdman, John Doe and Billy Zoom of X, Ross the Boss of the Dictators -- Angus Young is as deadly as eve