Photo: Spencer Platt/Getty Images Curtis Sliwa , the Republican candidate making his second run for mayor, is closing out the campaign the way he does everything: with restless energy, a bull-headed refusal to back down, and an endless string of wisecracks and wild, well-told anecdotes and observations accumulated during a lifetime spent roaming the streets of New York. But behind Sliwa’s constant patter is a plan. “Look, I start with 28 percent from the last election . I don’t think most of