HILADELPHIA, March 20 (AP) — The rate of suicides involving guns among black male teenagers nearly quadrupled from 1979 to 1994 before falling in the late 1990's, a study has found. The rate among white male teenagers climbed by more than a third from the late 1970's until the early 1990's before also falling. Traditionally, blacks have had much lower suicide rates than whites, but the availability of guns may help account for the narrowing of the gap among young men, researchers said. "One of the factors is the easy availability of firearms," said David Satcher, the former surgeon general...