ENH: remove reliance on the Xfer class (issue #639)

This class is largely a pre-C++11 holdover. It is now possible to
simply use move construct/assignment directly.

In a few rare cases (eg, polyMesh::resetPrimitives) it has been
replaced by an autoPtr.

src/sampling/meshToMesh/meshToMeshParallelOps.C

@@ -246,17 +246,12 @@ Foam::autoPtr<Foam::mapDistribute> Foam::meshToMesh::calcProcMap
         }
     }
 
-    autoPtr<mapDistribute> mapPtr
+    return autoPtr<mapDistribute>::New
     (
-        new mapDistribute
-        (
-            segmentI,       // size after construction
-            sendMap.xfer(),
-            constructMap.xfer()
-        )
+        segmentI,       // size after construction
+        std::move(sendMap),
+        std::move(constructMap)
     );
-
-    return mapPtr;
 }