mail-filter/opendkim: new revision to overhaul service scripts.

mail-filter/opendkim: new revision to overhaul service scripts.

The OpenRC service script has been largely rewritten in this revision,
to solve a number of problems:

  * The PID file is now stored securely (bug 629914).

  * Different PID files are used for multiple instances (bug 536162).

  * The detection of boolean options in the config file is more robust,
    allowing "1", "0", "yes", "false", et cetera.

  * The socket is now located in a conf.d file, rather than parsed from
    the config file. The service script ensures that the directory
    containing the socket has the correct permissions, and the conf.d
    file comes with a big warning to that effect. Note that the (commented-
    out) example directory IS NOT shared with the PID file.

  * An error is thrown if we can't remove a stale socket.

  * Modern OpenRC service script standards have been adopted.

Some minor changes have been made to the systemd service for
consistency, but none of them have been tested. More work needs to be
done here anyway; for example, we most likely want a tmpfiles.d entry
for the local socket directory if the user configures one. This should
be documented in opendkim.service.conf, and tested by someone who uses
systemd.

Closes: https://bugs.gentoo.org/536162
Bug: https://bugs.gentoo.org/629914
Signed-off-by: Michael Orlitzky <mjo@gentoo.org>
Package-Manager: Portage-2.3.62, Repoman-2.3.11