[3.1.1] Implement %URI.SecureMunge and %URI.SecureMungeSecretKey, thanks Chris!

- URIFilter->prepare can return false in order to abort loading of the filter
- Implemented post URI filtering. Set member variable $post to true to set a URIFilter as such.

git-svn-id: http://htmlpurifier.org/svnroot/htmlpurifier/trunk@1772 48356398-32a2-884e-a903-53898d9a118a

library/HTMLPurifier/AttrDef/URI.php

@@ -50,6 +50,10 @@ class HTMLPurifier_AttrDef_URI extends HTMLPurifier_AttrDef
             $result = $scheme_obj->validate($uri, $config, $context);
             if (!$result) break;
             
+            // Post chained filtering
+            $result = $uri_def->postFilter($uri, $config, $context);
+            if (!$result) break;
+            
             // survived gauntlet
             $ok = true;