Log Message:
Update to 1.6

Upstream changes:
1.6 2020-12-02

    - Fixed confusing Changes entry about Perl's licensing terms.
      [<KENTNL@cpan.org>, CPAN RT#132843]

    - Added optional Changes testing (skipped unless AUTHOR_TESTING).

    - Reformatted Changes file as per CPAN::Changes::Spec.

    - Added optional POD coverage testing (skipped unless AUTHOR_TESTING).

    - Added optional Perl::Critic testing (skipped unless AUTHOR_TESTING).

    - Made code Perl::Critic clean.

    - Added optional POD testing (skipped unless AUTHOR_TESTING).

    - Included GitHub repository URLs in metadata now that source code has been
      uploaded to GitHub (as of version 1.5).

    - Included META.json file in addition to META.yml.

    - Set minimum required ExtUtils::MakeMaker version to 6.64 to ensure that
      all parameters used are supported, to save jumping through hoops to
      support earlier versions.  (This should not be a problem since
      ExtUtils::MakeMaker 6.64 is easily installed into Perl 5.8.1 and above,
      that being the whole point of the new choice of minimum supported Perl
      version.)

    - Set minimum required Perl version to 5.8.1.  This is in line with the
      minimum requirement of the "Perl Toolchain".

    - Corrected typo in a comment.  [<dsteinbrunner@pobox.com>, CPAN RT#86336]