rename xfer<T> class to Xfer<T>

- The capitalization is consistent with most other template classes, but
  more importantly frees up xfer() for use as method name without needing
  special treatment to avoid ambiguities.

  It seems reasonable to have different names for transfer(...) and xfer()
  methods, since the transfer is occuring in different directions.
  The xfer() method can thus replace the recently introduced zero-parameter
  transfer() methods.
  Other name candidates (eg, yield, release, etc.) were deemed too abstract.

src/OpenFOAM/containers/HashTables/StaticHashTable/StaticHashTable.C

@@ -75,7 +75,7 @@ Foam::StaticHashTable<T, Key, Hash>::StaticHashTable
 template<class T, class Key, class Hash>
 Foam::StaticHashTable<T, Key, Hash>::StaticHashTable
 (
-    const xfer<StaticHashTable<T, Key, Hash> >& ht
+    const Xfer<StaticHashTable<T, Key, Hash> >& ht
 )
 :
     StaticHashTableName(),