Some content for tls_verify_cb where parts of our policy should
be implemented.
The rest of this change mostly contains random ideas taken from
mod_ssl. The purpose is to get the repository in sync with the
code I am testing. I still can't manage to make Netscape send
its certificate to slapd, though it works with Apache/mod_ssl
(with the same certificates). Trying s_client against both
does not shed any light. If anyone manages to make it work,
please let us know.