• Fix : It is now safe to call dispell() from inside 'free', 'copy' and
  'uvar' callbacks to dispell the magic currently in use.
  Thanks Clinton Gormley for reporting.
  
• Fix : Exceptions thrown from inside a 'free' callback are now always
  consistently propagated outside of the callback. They used to
  be lost when the 'free' callback was invoked at the end of an
  eval block or string.
  
• Fix : The 'reset RMG flag' workaroundn used to allow wizards with
  both 'uvar' and 'clear' magics to be cast onto a hash, has been
  made thread-safe.