/*
 * call-seq:
 *   Curl::Easy.http_head(url) { |easy| ... }         => #<Curl::Easy...>
 *
 * Convenience method that creates a new Curl::Easy instance with
 * the specified URL and calls +http_head+, before returning the new instance.
 *
 * If a block is supplied, the new instance will be yielded just prior to
 * the +http_head+ call.
 */
static VALUE ruby_curl_easy_class_perform_head(int argc, VALUE *argv, VALUE klass) {