ON THE EVE OF REVOLUTION, EGYPT IS A TINDERBOX. WILL ONE AMERICAN LIGHT THE SPARK THAT SETS IT ABLAZE?   Gore Vidal was one of America's greatest and most controversial writers.  The author of twenty-three novels, five plays, three memoirs, numerous screenplays and short stories, and well over two hundred essays, he received the National Book Award in 1993.   In 1953, Vidal had already begun writing the works that would launch him to the top ranks...