Agence France-Presse: A top oil executive admitted Tuesday that companies are ill-equipped to tackle major spills, as President Barack Obama readied for a solemn Oval Office address on the Gulf of Mexico catastrophe. In a stunning admission, ExxonMobil chief executive Rex Tillerson acknowledged in a series of testy exchanges with US lawmakers that oil giants are hamstrung once it comes to dealing with a major spill. “When these things happen, we are not well equipped to handle them,” he said, as …