[GH #851] Add pod_source_files to Parrot::Distribution and t/codingstd/copyright.t

This leads to several errors in the copyright.t tests
[codingstd][GH #851] Adapt copyright.t tests to POD files

skip book chapters since they contain an extra README.pod
skip empty t/tools/install/testlib/docs
skip bad_format test for bundled lib/Pod/*.pod since they are (C) with same terms as Perl.
skip duplicate (C) tests in .pod as they usually have the header plus a COPYRIGHT paragraph
[codingstd][GH #851] Add missing (C) lines to POD

Also update README_win32.pod content
[codingstd] ext/*.pod need a copyright but it can be from someone else
Merge branch 'rurban/pod-copyright-gh851'