MIDEAST STOCKS-Qatar, Saudi fall on Q2 earnings misses; FX troubles Egypt

* Commercial Bank of Qatar slumps 6.6 pct on Q2 earnings
* Saudi Electricity weighs on local market
* But major Saudi banks advance after earnings
* Egyptian pound sinks further in black market
* Emaar Properties pulls up Dubai
By Celine Aswad
DUBAI, July 20 (Reuters) – Stock markets in Qatar and Saudi Arabia were pulled lower on Wednesday by two blue-chip companies whose weak second-quarter earnings missed forecasts, while Egypt was hurt by a fresh slide of its currency in the black marke