Winnie Madikizela-Mandela, a controversial figure who served as a spearhead of South Africa’s anti-apartheid movement during husband and future president Nelson Mandela’s long imprisonment, died Monday at age 81. “Mrs. Madikizela-Mandela was one of the greatest icons of the struggle against apartheid,” Energy Minister Jeff Radebe said at a news conference at Johannesburg’s Netcare Milpark Hospital.…