/*
 * call-seq:
 *   easy.cookiefile = string                         => string
 *
 * Set a file that contains cookies to be sent in subsequent requests by this Curl::Easy instance.
 *
 * *Note* that you must set enable_cookies true to enable the cookie
 * engine, or this option will be ignored.
 */
static VALUE ruby_curl_easy_cookiefile_set(VALUE self, VALUE cookiefile) {