flnews: update to 0.16.

Provided by Michael B辰uerle in pkgsrc-wip.

Backported patches from 0.17 branch:
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          Bugfix: Configuration test result for inttypes.h presence is used,
            reintroduce the test
          Bugfix: BSD version of ntohl() for old systems now working again
          Modified LaTeX documentation to work with recent doxygen
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Changelog:
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V0.16      Bugfix: Supersede now preserves Followup-To header field
          Bugfix: The code that generates the attribute "reply to own article"
            now checks the Message-IDs too (to avoid errors if the parent
            article is missing in the hierarchy)
          Bugfix: Header parser and MIME parser fixed to correctly handle
            MIME entity delimiters (for boundary strings that contain spaces)
          Bugfix: Removed Unicode range U+E0020 ... U+E007E from rejected
            control characters (deprecated since Unicode 5.1, reintroduced for
            different purpose since Unicode 9.0) (Reported by Marcel Logen)
          TLS: Protocol version TLSv1.3 according to RFC8446 is now supported
            (requires at least OpenSSL 1.1.1)
          CORE module now supports multiple article hierarchies
          Unicode database updated to version 11.0.0
          IBM852 to UTF-8 converter added
          If the OS doesn't report IPv6 as available, usage can now be forced
            with the option 'CFG_FORCE_IP6'
          Support for reproducible builds added (option 'CFG_REPRODUCIBLE')
          Some checks for system header files removed to speed up configuration
            (Build fails in any case if they are missing)
          Documentation updated
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(wiz)