[InterNetNews/inn] 28f7cb: inews: Add a new flag to keep Sender untouched

[Julien ÉLIE]

  Branch: refs/heads/main
  Home:   https://github.com/InterNetNews/inn
  Commit: 28f7cb3e8475a6267a32ee833627a62daddfdb63
      https://github.com/InterNetNews/inn/commit/28f7cb3e8475a6267a32ee833627a62daddfdb63
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2022-02-19 (Sat, 19 Feb 2022)

  Changed paths:
    M doc/pod/inews.pod
    M doc/pod/news.pod
    M frontends/inews.c

  Log Message:
  -----------
  inews: Add a new flag to keep Sender untouched

inews no longer adds a Sender header field nor overwrites an existing one
in articles it processes if the new -s flag is used.

Without that possibility, its current behaviour is a bit irritating and not
useful.

see #158