KUALA LUMPUR (Reuters) - Malaysian opposition leader Anwar Ibrahim vowed on Tuesday to lead a "fierce movement" to reform the country's electoral system and challenge the results of an election he lost, starting with a rally of supporters this week. Anwar has refused to accept the victory of the long-ruling Barisan Nasional (BN) coalition in Sunday's election, saying that the result was tainted by widespread fraud, including the use of foreign immigrants to vote for the governing alliance. ...