* Main index up 71.93 points, or 0.6 percent, at 11,852.97 * Energy stocks lead rise as China policy eyed * U.S. and European central bank action also expected By Alastair Sharp TORONTO, Aug 9 (Reuters) - Resurgent energy and mining stocks on Thursday helped Canada's benchmark equity index regain ground it lost a day earlier as soft Chinese economic data kept alive talk that central bankers may ease monetary policy to stimulate growth. Shares in Canadian oil and gas companie