JOHANNESBURG (AFP) - Billions of dollars in aid will achieve "zero" in Africa unless governments on the continent are serious about fighting corruption and poverty, Irish rocker and humanitarian Bob Geldof said. The 54-year-old political activist, who will be performing in Johannesburg and Cape Town this week, said he saw "many, many optimistic signs and just as many crap signs" that African governments were cleaning up their act. "The rich world can pour endless billions into the continent of Africa but none of this will work unless African governments are serious," Geldof told a news conference in Johannesburg. "Corruption is...