By Chris Prentice and Tom Wilson WASHINGTON/LONDON (Reuters) -The U.S. dollar touched its highest level since 2002 on Thursday, as Wall Street rose and European shares moved off six-week lows as strong earnings reports offset gloomy U.S. economic data. The yen dropped to a 20-year low after the Bank of Japan vowed to buy unlimited amounts of 10-year bonds daily to defend its yield target. The bank’s strengthening of its commitment to ultra-low interest rates sent the U.S. dollar to a fresh high, weakened emerging market currencies and pushed borrowing costs for U.S. dollars in currency derivat…