fixed url escaping strategy for PHP 5.2

lib/Twig/Extension/Core.php

@@ -872,6 +872,10 @@ function twig_escape_filter(Twig_Environment $env, $string, $strategy = 'html',
             return twig_convert_encoding($string, $charset, 'UTF-8');
 
         case 'url':
+            if (version_compare(PHP_VERSION, '5.3.0', '<')) {
+                return str_replace('%7E', '~', rawurlencode($string));
+            }
+
             return rawurlencode($string);
 
         default: