• Add : Passing the signature of an already defined magic to wizard()
  now returns the corresponding magic object.
  
• Add : You can pass the numeric signature as the wizard argument of
  cast(), dispell() and getdata().
  
• Add : Any argument specified after the wizard (or the signature) in a
  call to cast() is now passed to the private data constructor in
  $_[1] and after.
  
• Chg : $_[0] is now always a reference to the magic variable in all
  callbacks. The reason for changing from the previous behaviour
  is that one may want to apply the same magic to a plain scalar
  and to a scalar reference, and needs a way to distinguish
  between them in the callback (say, ref()).
  
• Fix : Wizard object destruction used not to free the signature.