The Bionic Woman is back. Not to mention the Six Million Dollar Man. Together again for their second reunion television movie. If the producers have their way, The Bionic Showdown: Return of the Six Million Dollar Man and the Bionic Woman II, (at 8 tonight on KXAN-TV, Channel 36 Cable 4), will be a lead-in to a new weekly series with state-of-the-art bionics.