Saudi Arabia has led the way among major energy exporters in cutting oil production. At the same time, the kingdom is adding to global supply in a surprising way.  The deal to cut oil output has been a success, at least for its first month, largely because there was little cheating and because Saudi Arabia cut production by 500,000 barrels a day.  Don’t ignore the other side of the ledger, though: the Saudis, huge consumers of energy themselves, are economizing. That could allow them to export more.