Enable/disable global dns cache
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_USE_GLOBAL_CACHE,
Pass a long. If the enable value is 1, it tells curl to use a global DNS cache that will survive between easy handle creations and deletions. This is not thread-safe and this will use a global variable.
Subject for removal in the future. Do not use!
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.