mod_s2s_auth_dane: Fix traceback in DANE-TA check because unpack() moved It moved into the table package in Lua 5.2, error happens when compat is disabled or gone (ie 5.3+). This happened in DANE-TA, which is disabled by default.

<tr>
  <th>What is {x} {op} {y}?</th><td>
    <input name="captcha_challenge" type="hidden" value="{challenge}">
    <input name="captcha_reply" pattern="[0-9]+" required type="number">
  </td></tr>