The media columnist David Carr of The New York Times has died. Carr collapsed at the Times’ offices Thursday night and was pronounced dead shortly after. Hours before, he had moderated a panel discussion on the documentary “Citizenfour” along with director Laura Poitras, Glenn Greenwald, and the film’s lead subject, Edward Snowden. Carr overcame a major addition to crack cocaine in the late 1980s and went on to become a celebrated writer on media and culture. He was 58 years old.