/*
 * call-seq:
 *   easy.http_head                                   => true
 *
 * Request headers from the currently configured URL using the HEAD
 * method and current options set for this Curl::Easy instance. This
 * method always returns true, or raises an exception (defined under
 * Curl::Err) on error.
 *
 */
static VALUE ruby_curl_easy_perform_head(VALUE self) {