A fresh tumble of oil prices overnight looks likely to dampen Gulf stock markets on Thursday, while Egypt may continue testing technical resistance. Brent oil, hit by expectations that OPEC will keep its output ceiling unchanged at this week's meeting, sank more than 4 percent to below $43 a barrel overnight - to just above a six-year low. Also, hawkish comments by U.S. Federal Reserve Chair Janet Yellen reinforced the case for a U.S. interest rate hike later this month. ...