sasl: Fixed compilation warning in SSPI builds

/* The last #include file should be: */

#include "memdebug.h"

#ifndef CURL_DISABLE_CRYPTO_AUTH

#if !defined(CURL_DISABLE_CRYPTO_AUTH) && !defined(USE_WINDOWS_SSPI)

/* Retrieves the value for a corresponding key from the challenge string

 * returns TRUE if the key could be found, FALSE if it does not exists

 */