MIDEAST WEEKAHEAD-Oil, competition, Mobily hit Saudi earnings before bourse opens to foreigners

* Petchems, telecoms miss Q1 estimates * Banks outperform, cement makers match forecasts * Strong dollar hurts top consumer name Savola * But analysts hope petchems have bottomed out * Banks face tougher competition By Olzhas Auyezov DUBAI, April 23 (Reuters) - Despite a strong performance by banks, Saudi Arabia's first-quarter corporate earnings were generally weaker than expected, a sign that foreign investors should be cautious as the stock market opens up to them this year. The Capital Marke