johannesburg south african anti-apartheid veteran winnie madikizela-mandela ex-wife late president nelson mandela high spirit admit hospital minor surgery spokesman say thursday victor dlamini say statement 81-year-old former first lady admit hospital tuesday minor surgery knee doctor decide keep next two weeks recover visit hospital afternoon high spirit dlamini say conversation say health problems go back time banish brandfort apartheid government period knee first give trouble madikizela-mandela spend several weeks hospital last year back surgery ex-husband 27-year incarceration fight apartheid madikizela-mandela campaign release right black south africans undergo detention banishment arrest winnie mandela 'in high spirit minor surgery spokesman