GLOBAL MARKETS-Dollar wilts to 6-1/2 month low, shares gain

* Stocks notch up modest gains after U.S. data, earnings boosts* Major currencies locked in tight ranges, gold firm on safe-haven bid* Wheat hits 13 month high as Ukraine, Russia tensions simmer* China yuan firms, talk of central bank intervention helpsBy Marc JonesLONDON, May 6 (Reuters) - The dollar fell to a 6-1/2 month low on Tuesday despite signs the U.S. economy is emerging from a particular