By Elizabeth Howcroft and Koh Gui Qing NEW YORK/LONDON (Reuters) -Global stocks fell on Thursday as recession concerns and the Russian-Ukranian war curbed demand for risky assets, while oil prices plunged over $5 on news that the United States may release some of its emergency oil reserves. With Thursday’s drop, U.S. and European stocks are set for their worst quarterly performance since the first quarter of 2020, when the outbreak of the COVID-19 pandemic briefly sent the global economy into a tailspin. Quarter-end rebalancing of portfolios boosted demand for bonds and held down yields, thoug…