[InterNetNews/inn] 180e8e: Do not include config.h in installed header files

[Julien ÉLIE]

  Branch: refs/heads/main
  Home:   https://github.com/InterNetNews/inn
  Commit: 180e8e78afecf884f565c2cfee9f5ddd999f71c8
      https://github.com/InterNetNews/inn/commit/180e8e78afecf884f565c2cfee9f5ddd999f71c8
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2022-09-10 (Sat, 10 Sep 2022)

  Changed paths:
    M include/Makefile
    M include/portable/stdbool.h
    M support/getrra-c-util

  Log Message:
  -----------
  Do not include config.h in installed header files

Including inn/storage.h in an external program makes its build fail
because of the inclusion of config.h from inn/portable-stdbool.h
unless CONFIG_H_INCLUDED is defined.
This behaviour can be improved: we now unconditionaly include config.h
in portable/stdbool.h, and inn/system.h in inn/portable-stdbool.h.

This fixes the build of external programs like newsx (where that issue was
detected).