TYSON WINS W.B.C. CHAMPIONSHIP LAS VEGAS, Nev., Nov. 22— Mike Tyson made history tonight. The 20-year-old slugger from Catskill, N.Y., became the youngest heavyweight champion ever when he stopped Trevor Berbick at 2:35 of the second round of a scheduled 12-round bout. In taking away Berbick's World Boxing Council crown, Tyson knocked Berbick down twice, both times in the second round, pounding him so hard that he had Berbick reeling across the ring at the end in a nearly comic loop-de-loop.