WAIT, WAIT, THERE'S MORE . . . The official program was over at a meeting of former African heads of state at the John F. Kennedy Presidential Library on Wednesday night, but the party wouldn't quit. Zambia's former president Kenneth Kaunda grabbed the microphone and a guitar and began singing. Then former Ghana president Jerry Rawlings took over and told jokes. Phylicia Rashad MC'd the African Presidential Roundtable 2005, presented by the African Presidential Archives and Research Center at Boston University.