The Elton John Pontiac Stadium show was a pleasant surprise in many ways, and a predictable let-down in others. After a competent opening by John Miles, Elton hit the stage to do what he's really good at; entertaining audiences by making fun of himself, presenting a visually arresting show and keeping the music driving fast enough to keep everybody on the edge of their seats. Elton was supported by three uninhibited, sassy soccef-gear-clad dancer/singers; two boys and a girl named Tex who seemed to have no end of energy. The combination of them and this short, balding man screaming like a silly girl, -dressed in a green glitter coat, with