HALLOWEEN H20: TWENTY YEARS LATER (1998, USA, 86m, 18) *** Horror, Thriller dist. Dimension Films (USA), Buena Vista Interna-tional (UK); pr co. Dimension Films / Nightfall Productions / Trancas International Films; d. Steve Miner; w. Robert Zappia, Matt Greenberg (based on a story by Robert Zappia and characters created by Debra Hill and John Carpenter);…