Global stocks and U.S. futures held steady Tuesday after escalating concerns about the economic impact of the coronavirus triggered a sharp selloff on Wall Street a day earlier. Futures tied to the S&P 500 and the Dow Jones Industrial Average were 0.5% and 0.4% higher, respectively. The pan-continental Stoxx Europe 600 and the German DAX were both flat, having fallen more than 3% Monday. The…