GLOBAL MARKETS-Stocks head for worst quarter since euro crisis, dollar reigns

* Share markets mixed amid uncertainty over Hong Kong, quarter end * Euro zone awaits inflation data * HSBC manufacturing survey disappoints, but exports improve * Dollar holds hefty gains for the month, pressures commodities By Marc Jones LONDON, Sept 30 (Reuters) - World markets were in hesitant mood on Tuesday as investors wondered what China's response would be to civil unrest in Hong Kong, while the U.S. dollar eased off the throttle after its biggest quarterly gain in