ATLANTA — A man who dredges his art up through a reservoir of phlegm, subterranean myth, vaudevillian shtick, fractured blues, and the fantastic testimony of a carnival barker, Tom Waits has long served as a kind of all-purpose synonym: He’s a one-man signifier of vintage American weirdness, whose gruff veneer gives way to soulful depths of tear-wringing melancholy.