Add structured output to http-auth.nse.

scripts/http-auth.nse

@@ -23,6 +23,23 @@ authentication.
 -- |   Digest charset=utf-8 nonce=+Upgraded+v1e4e256b4afb7f89be014e...968ccd60affb7c qop=auth algorithm=MD5-sess realm=example.com
 -- |_  Basic realm=example.com
 --
+-- @xmloutput
+-- <table>
+--   <elem key="scheme">Basic</elem>
+--   <table key="params">
+--     <elem key="realm">Router</elem>
+--   </table>
+-- </table>
+-- <elem key="scheme">Digest</elem>
+--   <table key="params">
+--     <elem key="nonce">np9qe4zJBAA=1f3ae82f536e70a806241b3358f571507a3a4d67</elem>
+--     <elem key="realm">Router</elem>
+--     <elem key="algorithm">MD5</elem>
+--     <elem key="qop">auth</elem>
+--     <elem key="domain">secret</elem>
+--   </table>
+-- </table>
+--
 -- @args http-auth.path  Define the request path
 
 -- HTTP authentication information gathering script
@@ -82,5 +99,5 @@ action = function(host, port)
     table.insert(result, line)
   end
 
-  return stdnse.format_output(true, result)
+  return challenges, stdnse.format_output(true, result)
 end