FOREX-Dollar gains after relatively strong data, Aussie dollar tumbles
* U.S. dollar strengthens to fresh three-week high * Aussie dollar has biggest single-day decline since March * Focus on yen, shift in BoJ's yield curve control policy (Updates prices to 4:14 p.m.) By Herbert Lash NEW YORK, Aug 1 (Reuters) - The dollar advanced against major currencies on Tuesday af...