Manually apply PR #1594 (fixing phpdoc page-level generation/warnings)

Also partially fixes issue #1295, fixes inconsistencies in some page-level docblocks and adds include checks in language files.
diff --git a/system/helpers/captcha_helper.php b/system/helpers/captcha_helper.php
index 3aac14d..e9b167f 100644
--- a/system/helpers/captcha_helper.php
+++ b/system/helpers/captcha_helper.php
@@ -1,4 +1,4 @@
-<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+<?php
 /**
  * CodeIgniter
  *
@@ -24,6 +24,7 @@
  * @since		Version 1.0
  * @filesource
  */
+defined('BASEPATH') OR exit('No direct script access allowed');
 
 /**
  * CodeIgniter CAPTCHA Helper