Zimbabwe opposition reunites to challenge Mugabe

By MacDonald DzirutweHARARE (Reuters) - Zimbabwe's main opposition leader Morgan Tsvangirai on Saturday reunited with his former allies to agree a pre-election pact to challenge President Robert Mugabe's near four-decade hold on power at the polls next year.Mugabe, 93, has ruled the former British colony since independence in 1980.Tsvangirai's Movement for Democratic Change (MDC) has been the main threat to Mugabe since its formation in 1999 but has been weakened by splits, in 2005 and 2014, mai