Remove passwd handler from struct when not needed

CURLOPT_PASSWDFUNCTION was removed in cURL 7.15.5, the passwd field
will not be used for version greater than this one

Author: adoy

ext/curl/interface.c

@@ -3267,9 +3267,11 @@ static void _php_curl_close_ex(php_curl *ch TSRMLS_DC)
 	if (ch->handlers->write_header->func_name) {
 		zval_ptr_dtor(&ch->handlers->write_header->func_name);
 	}
+#if CURLOPT_PASSWDFUNCTION != 0
 	if (ch->handlers->passwd) {
 		zval_ptr_dtor(&ch->handlers->passwd);
 	}
+#endif
 	if (ch->handlers->std_err) {
 		zval_ptr_dtor(&ch->handlers->std_err);
 	}

ext/curl/php_curl.h

@@ -135,7 +135,9 @@ typedef struct {
 	php_curl_write *write;
 	php_curl_write *write_header;
 	php_curl_read  *read;
+#if CURLOPT_PASSWDFUNCTION != 0
 	zval           *passwd;
+#endif
 	zval           *std_err;
 	php_curl_progress *progress;
 #if LIBCURL_VERSION_NUM >= 0x071500 /* Available since 7.21.0 */