GRAINS-Corn, soy at two-week highs on hot weather worries

* Corn, soybeans hit highest levels since late July * Stressful weather seen in parts of U.S. and Europe * USDA expected to trim U.S. corn, soy yields this week * Wheat follows higher trend (Adds weekly USDA crop ratings, closing prices) By Julie Ingwersen CHICAGO, Aug 10 (Reuters) - Chicago Board of Trade corn and soybean futures climbed to two-week highs on Monday amid concerns about stressful hot weather in the United States and Europe coupled with positioning ahead of a