Update from version 1.22 to 1.25.  Changes:

1.25, 22 Jul 2008 ^

    * Portability: support Perls before 5.7.3, and make this
      dependency explicit in the Makefile.PL

1.24, 20 Jul 2008 ^

    * Remove threads test which had inadvertantly slipped into the
      MANIFEST from source control, and add comprehensive documentation
      on the state of thread support in this module.
    * Correct other silly MANIFEST mistakes.

1.23, 18 Jul 2008 ^

    * Make behaviour when dealing with items which were undef
      defined. Previously it might segfault (or Bus Error on Mac OS
      X) on some operations and Perl versions, or result in an empty
      string being inserted.
    * Fix a minor compile problem on IRIX, reported by David Cantrell.

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