- 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.

- this should provide a slightly more naturally means to using transfer
  constructors, for example
          labelList list2(list1.transfer());
      vs. labelList list2(xferMove(list1));

- returns a plain list where appropriate (eg, DynamicList, SortableList)
  for example
          labelList list2(dynList1.transfer());
      vs. labelList list2(xferMoveTo<labelList>(dynList1));

usage of the public 'label& List::size()'.

IMO this method is much too dangerous to leave public - the different
signature is needed to avoid confusing the compiler.

because I failed to work out how to merge Mark's stuff -- HELP!!!