cpdup - Add another way to prevent host:path misintepretation

cpdup - Add another way to prevent host:path misintepretation

* Allow a local file or directory name to be prefixed with localhost:
  to prevent colons in the filename from being misinterpreted as a
  remote-host specification.

  This is in addition to the nominal absolute-path method to prevent
  misinterpretation (a '/' occuring before any ':' prevents
  misinterpretation of the ':' as a remote-host specification)