European shares rise; retailers gain as results spur mergers talk* FTSEurofirst 300 up 0.2 pct, Euro STOXX 50 up 0.6 pct* Euro STOXX 50 now at 2-month low as euro zone woes mount* Standard Chartered stock hits record low, but UBS upgrades* AB InBev, Carrefour hit by broker downgradesBy Blaise RobinsonPARIS, Oct 23 European shares inched up in early trade on Wednesday, reversing early losses on M&A talk in the retail sector, while strong results from brewer AB InBev also spurred the sector's rebound.Standard Chartered shares fell more than 7 percent, hitting a record low, after the Asia-focused bank