[InterNetNews/inn] 525e13: Use pod2text --guesswork when the option is available

[Julien ÉLIE]

  Branch: refs/heads/2.7
  Home:   https://github.com/InterNetNews/inn
  Commit: 525e13ee3e6cebcadf4d8dcba173d1f7b5ecaad9
      https://github.com/InterNetNews/inn/commit/525e13ee3e6cebcadf4d8dcba173d1f7b5ecaad9
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2022-12-26 (Mon, 26 Dec 2022)

  Changed paths:
    M Makefile.global.in
    M configure.ac

  Log Message:
  -----------
  Use pod2text --guesswork when the option is available

New in podlators 5.01 recently published, this option permits disabling
heuristics which prevent some patterns from being converted as expected.

Improve the Autoconf check so that it does not rely on the exit status of
the --help command.