(ITS#9086) Add debug logging for GnuTLS configuration errors

[ryan@openldap.org]

Full_Name: Ryan Tandy
Version: master
OS: Debian 10/buster
URL: https://github.com/openldap/openldap/compare/master...rtandy:gnutls-logging.patch
Submission from: (NULL) (70.66.128.207)
Submitted by: ryan


This patch adds debug logging for common GnuTLS configuration errors. It should
help with troubleshooting issues such as slapd failing to start due to incorrect
paths or permissions, or client TLS connections failing if the CA file can't be
read.

Posting here for review. I'll upload this to Debian as well and try to get some
feedback from users.

-- 

The attached patch file is derived from OpenLDAP Software. All of the
modifications to OpenLDAP Software represented in the following patch(es) were
developed by Ryan Tandy <ryan@nardis.ca>. I have not assigned rights and/or
interest in this work to any party.

I, Ryan Tandy, hereby place the following modifications to OpenLDAP Software
(and only these modifications) into the public domain. Hence, these
modifications may be freely used and/or redistributed for any purpose with or
without attribution and/or other notice.