/*
 * call-seq:
 *   easy.url = "http://some.url/"                    => "http://some.url/"
 *
 * Set the URL for subsequent calls to +perform+. It is acceptable
 * (and even recommended) to reuse Curl::Easy instances by reassigning
 * the URL between calls to +perform+.
 */
static VALUE ruby_curl_easy_url_set(VALUE self, VALUE url) {