Update to 0.006
    
    - New upstream release 0.006
      - EXPERIMENTALLY provide Test::Lib-like behavior, and a related -lib export
        tag
      - Support an environment variable PERL_TEST_MODERN_ALLOW_WARNINGS to allow
        end-users to skip running end warnings tests
      - Added shouldnt_warn function
    - Add upstream workaround for warnings generated in File::Spec