Hagley Museum’s Alfresco dining nights on Thursdays in May will include a variety of cuisines. Photo by Kerry Harrison.   You would expect to see 19th century tools and the du Pont ancestral home and gardens at Hagley Museum and Library, the birthplace of Eleuthère Irénée du Pont’s gunpowder works. Flatbread and couscous, however, may come as a surprise. The Middle …