ANGE ABOA IVORY Coast President Alassane Ouattara has rejected calls for negotiations from rivals urging a boycott of an October 31 election they say he should not be standing for. Ouattara's main challengers, ex-President Henri Konan Bedie and ex-prime minister Pascal Affi N'Guessan, accuse the 78-year-old former International Monetary Fund (IMF) economist of violating the constitution by standing for a third term. Protests against Ouattara's candidacy have killed more than a dozen people since August. Thousands of cheering supporters greeted Ouattara in Bouake, the capital of the rebellion that swept him to power in 2011 after a disputed election, as…