John Silber, the sharp-tongued, pugnacious public intellectual who transformed Boston University during a quarter-century as president and mounted an unsuccessful run for governor of Massachusetts, died Thursday. He was 86, the Associated Press reports. Silber died of kidney failure at his Brookline home, BU spokesman Colin Riley said. Silber took over BU, then a financially troubled commuter school of middling reputation, in 1971 and used his forceful — some said imperious — personality to remake it into a prominent national university…