SHANGHAI/HONG KONG (Reuters) – China stepped up its crackdown on short-selling of shares on Tuesday, unveiling rules that make it harder for speculators to profit from hourly price changes, as some of the nation’s major brokerages suspended their short-selling businesses. China’s stock exchanges and market watchdogs are cracking down on short-selling as part of a broad government-orchestrated effort to prevent a collapse in the country’s markets, which have lost about 30 percent of their value since peaking in June.