configure: detect the broken poll() in macOS 10.12

#                            | (__| |_| |  _ <| |___

#                             \___|\___/|_| \_\_____|

#

# Copyright (C) 1998 - 2013, Daniel Stenberg, <daniel@haxx.se>, et al.

# Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.

#

# This software is licensed as described in the file COPYING, which

# you should have received as part of this distribution. The terms

      AC_LANG_PROGRAM([[

        $curl_includes_stdlib

        $curl_includes_poll

        $curl_includes_time

      ]],[[

        /* detect the original poll() breakage */

        if(0 != poll(0, 0, 10))

          exit(1); /* fail */

        else

          exit(0);

        else {

          /* detect the 10.12 poll() breakage */

          struct timeval before, after;

          int rc;

          size_t us;

          gettimeofday(&before, NULL);

          rc = poll(NULL, 0, 500);

          gettimeofday(&after, NULL);

          us = (after.tv_sec - before.tv_sec) * 1000000 +

            (after.tv_usec - before.tv_usec);

          if(us < 400000)

            exit(1);

        }

      ]])

    ],[

      AC_MSG_RESULT([yes])