MIDEAST STOCKS-Small-caps pull down Saudi, Egypt slides

* Saudi petchems hold up well after slide on budget * But margin calls hit speculative shares hard * Almarai tumbles after forecasting higher costs * Egypt sinks as it reopens after holiday * Qatar underperforms UAE bourses By Andrew Torchia DUBAI, Jan 10 (Reuters) - A sell-off of small-cap speculative stocks pulled Saudi Arabia's stock market down on Sunday, while Egypt dropped in response to weak global equities and concern about risks to the Chinese economy. Most Gulf markets were subdued. Th