Update Test-Harness to CPAN version 3.27

  [DELTA]

  3.28    2013-05-02
          - Bugfix: Fix taint failures on Windows (Jan Dubois)

  3.27    2013-04-30
          - Dramatically reduce memory usage (Nick Clark, RT #84939)
          - Store test_num (in Grammar.pm) as a number instead of a string.
            Reduces memory usage (Nick Clark, RT #84939)
          - PERL5LIB is always propogated to a test's @INC, even with taint more
            (Schwern, RT #84377)

The local modifications to t/source.t are retained. [rt.cpan.org #64353]