Somewhat slow of step, but sharp as a tack, former Gov. Hugh Carey, 90, lunched the other day at Kennedy’s Saloon on West 57th Street with William Flynn, the former Mutual of Omaha chairman and hero of the Northern Ireland Peace Accords. Carey, leaning lightly on a cane, was escorted to Flynn’s limo by a comely blond hostess. As he made his way past the bar, a wag yelled out, “Hey, Gov, you always have a good-looking dame on your arm!” Carey’s eyes lit up and it looked, for a moment, like he was going to launch into “Danny Boy.”