don't do SO_KEEPALIVE, we already have a finer grained method built-in

   return informational stuff as errors, consider a new info returned by

   curl_easy_getinfo() #845941

 * Option to set the SO_KEEPALIVE socket option to make libcurl notice and

   disconnect very long time idle connections.

 LIBCURL - multi interface

 * Add curl_multi_timeout() to make libcurl's ares-functionality better.