NEW YORK (Reuters) - The biggest tumble in Chinese stocks in more than eight months led global equity markets lower Thursday as concern mounted about a new coronavirus outbreak in China.Millions of Chinese are preparing to travel for the Lunar New Year which begins on Saturday, increasing the potential for the disease to spread. The cities of Wuhan and Huanggang, representing a total population of about 18 million people, were put on a travel lockdown to prevent the virus from spreading, a..