MIDEAST STOCKS-Gulf falls on oil and earnings, Egypt hit by FX worries

* Emaar Properties fails to break technical resistance * Saudi's Yamama Cement tumbles on earnings, dividend cut * But petchems strong, Yanbu climbs after Q2 earnings beat * Widespread selling of banks pulls down Qatar * Gap between official, unofficial Egypt FX rates hits record By Andrew Torchia DUBAI, July 21 (Reuters) - Most Gulf stock markets fell on Thursday amid soft oil prices and mixed corporate earnings, while Egypt was hit once again by concern about instability in the country's curre