ENH: snappyHexMesh: switch on multipatch snapping

tutorials/mesh/snappyHexMesh/flange/system/snappyHexMeshDict

@@ -186,6 +186,10 @@ snapControls
 
         //- Use castellatedMeshControls::features
         explicitFeatureSnap true;
+
+        //- Detect features between multiple surfaces
+        //  (only for explicitFeatureSnap, default = false)
+        multiRegionFeatureSnap true;
 }