[InterNetNews/inn] d7f1e8: Add link to LibreSSL, and use function from 3.6.0

[Julien ÉLIE]

  Branch: refs/heads/main
  Home:   https://github.com/InterNetNews/inn
  Commit: d7f1e80e3ad79037f3e44033f711673617242e30
      https://github.com/InterNetNews/inn/commit/d7f1e80e3ad79037f3e44033f711673617242e30
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2023-03-05 (Sun, 05 Mar 2023)

  Changed paths:
    M doc/pod/hacking.pod
    M nnrpd/tls.c

  Log Message:
  -----------
  Add link to LibreSSL, and use function from 3.6.0

All of the OpenSSL API we're using is available in latest releases of
LibreSSL.
Building INN with LibreSSL 3.6.2 (released) and 3.7.0 (still
in development) is OK, as well as OpenSSL 3.0.8 (released) and
3.1.0-beta1.