After more than a year of mixed signals, the mining company Anglo American P.L.C., which is confronted with a crushing AIDS burden in Africa, said today that it would begin supplying life-prolonging drugs to all its employees who are H.I.V. positive...The rates of H.I.V. infection among adults in Botswana, Namibia, South Africa and Zimbabwe - countries where Anglo operates - are among the highest in the world.