Warren Zevon, Monday, January 15, at the Bluebird Theater, has a sense of humor twisted enough to appreciate the downturn in his commercial fortunes. Appearing on the scene with a self-titled album in 1976, Zevon burned brighter than almost any of his fellow Southern California songwriters: His first four or five albums found him combining his sturdy musical skills with a nasty sense of humor and a worldview as nervy as it was disturbing. But remaining on the edge for so long proved impossible, and Zevon hasn't been quite the same since he cleaned himself up. That could change, however: Now that he's been dropped by his latest record label (Giant), Zevon may hit town with his old juices flowing again. And even if he doesn't, he can still turn in a pretty mean version of "Roland the Headless Thompson Gunner."