“Too often, big stage deals have hit the screen, large or small, with an audible thud, making viewers wonder what was so special about the originals anyway. For some of us, “Angels in America” is a happier story. Building on his astute and graceful 2001 HBO adaptation of the Margaret Edson play “Wit,” director Mike Nichols has taken the hospital bed so prominent in that drama, about a cancer patient, and wheeled it over to another, more expansive wing.”