This backend provides Active Directory details for current user. If
the system is not part of Active Directory domain, GetUserNameEx is
used instead, so at least user (given) name is configured.

Unlike ldap backend, this one doesn't need connection configuration,
as the used API works with current user security context.

Change-Id: I74bcc79591a658dc5121df1f09caa15d272fbe12
Reviewed-on: https://gerrit.libreoffice.org/53590Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>