/*
 * call-seq:
 *   easy.cookiejar = string                          => string
 *
 * Set a cookiejar file to use for this Curl::Easy instance.
 * Cookies from the response will be written into this file.
 *
 * *Note* that you must set enable_cookies true to enable the cookie
 * engine, or this option will be ignored.
 */
static VALUE ruby_curl_easy_cookiejar_set(VALUE self, VALUE cookiejar) {