MIDEAST STOCKS-Qatar outperforms, rest of region sluggish

* Volumes low across region as oil, global markets cool * Qatar supported by blue chips * Aramex extends gains in Dubai * Saudi flat as petchems, bank shares mixed * Egypt slips as shares favoured by foreigners decline By Celine Aswad DUBAI, Aug 29 (Reuters) - Qatar's stock market outperformed the Gulf on Monday as large-caps carried the index higher, but other bourses were little changed as a fresh slide in oil prices and a retreat in Asian share markets kept buyers away. Qatar's main index add