• Add : The 'copykey' option to wizard(), that enables the safe edition
  of $[2] in uvar callbacks to redirect actions to another key.
  
• Fix : Exception objects thrown from callbacks at compile time were not
  available in $@.
  
• Fix : free callbacks triggered during global destruction could lead to
  segfaults because the wizard was already freed.
  
• Fix : Refcount of scalars with free callback.
  
• Fix : Segfaults when using get or uvar magic simultaneously with clear
  magic.
  
• Doc : The documentation about what the callbacks take and should
  return is now somewhat clearer.