ATHENS (Reuters) - Standard & Poor's said on Thursday it would keep its long-term foreign sovereign credit rating for Greece at selective default until the country's bond swap is fully concluded. Earlier this week, Fitch became the first ratings agency to move Greece out of default territory, assigning the country a speculative B- rating. But S&P said it would likely raise its rating to CCC - extremely speculative - only once Greece's debt restructuring is completed next month, with an exchange of bonds governed by international law. ...