By Tannur Anders and Sfundo Parakozov JOHANNESBURG (Reuters) -South Africans angry at joblessness, inequality and power shortages slashed support for the African National Congress (ANC) to 40% in this week’s election, ending three decades of dominance by the party that freed the country from apartheid. A dramatically weakened mandate for the legacy party of Nelson Mandela, down from the 57.5%…