• Some attempts at code readability, increased logging level for fallback cert generation that
  was swept under the DEBUG carpet before.
• More verbosity when not handing out certificates, e.g. mod_ssl asks, but mod_md has no
  idea what it is talking about. Some people report misbehaviour here.
• Re-enabled support for md_get_credentials() function that was used in older mod_ssl
  patch, so that people with old patched servers get a chance to upgrade.