test order 2 geo on nodes

DiffractionGratings/grating2D.geo

@@ -256,4 +256,7 @@ EndIf
 
 Solver.AutoMesh=1;
 Geometry.Points = 0;
-Mesh.SurfaceEdges = 0;
\ No newline at end of file
+Mesh.SurfaceEdges = 0;
+// Mesh.SecondOrderLinear = 1;
+Mesh.SecondOrderExperimental = 1;
+Mesh.MshFileVersion = 2;