Assemble polygons from imported groups too; so that lets you draw a

section, import it, and extrude it.

[git-p4: depot-paths = "//depot/solvespace/": change = 1859]

groupmesh.cpp

@@ -20,7 +20,7 @@ void Group::GeneratePolygon(void) {
     poly.Clear();
 
     if(type == DRAWING_3D || type == DRAWING_WORKPLANE || 
-       type == ROTATE || type == TRANSLATE)
+       type == ROTATE || type == TRANSLATE || type == IMPORTED)
     {
         if(AssemblePolygon(&poly, &(polyError.notClosedAt))) {
             polyError.how = POLY_GOOD;