Forget the Disney/Spielberg pedigree: The most important merger in the making of The BFG is the reunion of the director with Melissa Mathison, who wrote the screenplay for 1982’s E.T. the Extra-Terrestrial. While The BFG is a faithful adaptation of the 1982 children’s book by Roald Dahl, there are decided parallels between Mathison’s two scripts, which each hinge on the friendship between a melancholy child and a powerful, benign nonhuman…