[InterNetNews/inn] 736fa8: Add new gencancel program

[Julien ÉLIE]

  Branch: refs/heads/main
  Home:   https://github.com/InterNetNews/inn
  Commit: 736fa80f93b6421160e791c2f5c116db4e5cf6c8
      https://github.com/InterNetNews/inn/commit/736fa80f93b6421160e791c2f5c116db4e5cf6c8
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2022-02-24 (Thu, 24 Feb 2022)

  Changed paths:
    M .gitignore
    M MANIFEST
    M control/Makefile
    A control/gencancel.c
    M doc/man/Makefile
    M doc/pod/Makefile
    A doc/pod/gencancel.pod
    M doc/pod/inn-secrets.conf.pod
    M doc/pod/news.pod
    M support/mkmanifest

  Log Message:
  -----------
  Add new gencancel program

It will notably be useful for news administrators, as this program will
generate authenticated cancel control articles with admin Cancel-Key hashes.

Add a man page for it.

Cancel-Lock support seems now complete in INN.

close #47 (finally!)