[InterNetNews/inn] ce56c5: pullnews: Correctly find the end of headers

[Julien ÉLIE]

  Branch: refs/heads/main
  Home:   https://github.com/InterNetNews/inn
  Commit: ce56c522eb2128f034b6511ae413df351a6b9775
      https://github.com/InterNetNews/inn/commit/ce56c522eb2128f034b6511ae413df351a6b9775
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2023-04-16 (Sun, 16 Apr 2023)

  Changed paths:
    M frontends/pullnews.in

  Log Message:
  -----------
  pullnews: Correctly find the end of headers

A mere LF was looked at, instead of CRLF.  It notably breaks the
removal of the last header field (usually Xref) with -H.

For a header feed, also add CRLF at the end of the headers, and not a
mere LF.