By Sinéad Carew and Amanda Cooper NEW YORK/LONDON (Reuters) -MSCI’S global equities index gained very slightly as investors digested a mixed crop of earnings reports and waited for key economic releases due later in the week while the yen fell after the Bank of Japan left monetary policy unchanged. While the dollar index climbed to a six-week high, U.S. Treasury yields rose as investors waited for economic growth and inflation data for clues on when the Federal Reserve will decide to cut interest rates. Oil prices on Tuesday handed back some of the previous day’s gains, as traders weighed prod…