Though it bent (and blew) the minds of rapt audiences with its elusive opalescence nearly three decades ago, David Henry Hwang's 'M. Butterfly' returns to Broadway on heavier, drabber wings. True, the revival that opened on Thursday night at the Cort Theater, directed by Julie Taymor, has basically the same anatomy as its predecessor. But it has undeniably morphed into a more prosaic creature, and the tantalizing mists that surrounded its initial run have dissolved as if under a harsh morning sun. When the enigmatic title character in this breakthrough drama about the illusions of sexual and cultural identity is brusquely commanded to 'Strip!' by a stricken suitor, you're apt to think, 'No need guys. That's already been taken care of.'