GLOBAL MARKETS-Stocks tumble, oil surges on Yemen air strikes

(Adds Wall Street drop, latest prices) * Stocks fall in America, Europe and Asia * Oil rises on fears of Middle East supply disruption * Dollar retreats versus yen, euro * Gold tops $1,200 an ounce By Michael Connor NEW YORK, March 26 (Reuters) - Stock markets around the world were knocked lower and oil prices jumped as much as 6 percent on Thursday after Saudi Arabia and its allies carried out air strikes in Yemen that also stung the dollar. Key indexes on Wall S