[Routing] use faster approach for encoding rel segments

replaced the preg_replace code that was 1.4 times slower than the new code (verified with benchmark

src/Symfony/Component/Routing/Generator/UrlGenerator.php

@@ -189,7 +189,12 @@ protected function doGenerate($variables, $defaults, $requirements, $tokens, $pa
         // the path segments "." and ".." are interpreted as relative reference when resolving a URI; see http://tools.ietf.org/html/rfc3986#section-3.3
         // so we need to encode them as they are not used for this purpose here
         // otherwise we would generate a URI that, when followed by a user agent (e.g. browser), does not match this route
-        $url = preg_replace(array('#/\.\.(/|$)#', '#/\.(/|$)#'), array('/%2E%2E$1', '/%2E$1'), $url);
+        $url = strtr($url, array('/../' => '/%2E%2E/', '/./' => '/%2E/'));
+        if ('/..' === substr($url, -3)) {
+            $url = substr($url, 0, -2) . '%2E%2E';
+        } elseif ('/.' === substr($url, -2)) {
+            $url = substr($url, 0, -1) . '%2E';
+        }
 
         // add a query string if needed
         $extra = array_diff_key($originParameters, $variables, $defaults);