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In a few rare cases (eg, polyMesh::resetPrimitives) it has been
replaced by an autoPtr.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/functionObjects/field/streamLine/streamLineBase.C

@@ -655,8 +655,8 @@ bool Foam::functionObjects::streamLineBase::write()
         const mapDistribute distMap
         (
             globalTrackIDs.size(),
-            sendMap.xfer(),
-            recvMap.xfer()
+            std::move(sendMap),
+            std::move(recvMap)
         );