EMERGING MARKETS-Brazil stocks rise after holiday, commodities fly

* After holiday, Bovespa tracks foreign markets' Tuesday gain * OGX rises for fourth straight day * Brazil Bovespa up 0.9 pct, Mexico IPC down 0.3 pct By Lucas Iberico-Lozada and Asher Levine SAO PAULO, July 10 (Reuters) - Brazilian stocks opened higher on Wednesday following a market holiday in the previous session, led by commodities exporters' shares. Mexico's IPC index fell for the third session in four, while Chile's bourse dropped for the fourth straight day. Brazi