SACRED STONE Clive Cussler debuted his new series, The Oregon Files, with the incredible adventure of Golden Buddha. Now he follows that triumph with Sacred Stone, a rollicking new tale featuring the enigmatic captain of The Oregon, Juan Cabrillo.   In the remote wastes of Greenland, an ancient artifact possessing catastrophic radioactive power is unearthed. But the astounding find puts the world at risk.   Caught between two militant factions bent on wholesale slaughter, Juan Cabrillo and his network of spies known as The Corporation must fight to protect the stone-and prevent the outbreak of World War III.