GLASGOW (Reuters) - Britain's ruling Labour Party lost a parliamentary seat in one of its traditional strongholds, a stinging electoral setback for Prime Minister Gordon Brown, results showed on Friday. Defeat in Thursday's poll in the Glasgow East constituency, which Labour won with a huge 13,500 majority at the 2005 election, will fuel Labour discontent with Brown's leadership and could lead to moves to oust him, some analysts believe. The pro-independence Scottish National Party (SNP) scored a dramatic victory by a slim 365-vote margin as voters in Britain's third-largest city turned against Labour in droves. The result, following a series...