WASHINGTON (Reuters) -U.S. market regulators began the process of furloughing workers on Wednesday as the federal government shut down after Congress failed to extend funding, curtailing key oversight functions, stymieing initial public offerings, and limiting some market and economic data. The shutdown, which began at midnight, will force the Securities and Exchange Commission to furlough more than 90% of its workforce, retaining only about 393 employees to handle emergency enforcement actions and market ...