Don't use globals

- Use load_class() to get objects during bootstrap process.
- Change load_class() to accept a class constructor parameter
  instead of previously unused class name prefix.
- Change CI_Router::__construct() to accept  as a parameter.
diff --git a/system/core/URI.php b/system/core/URI.php
index 5f5a9ce..9a545fd 100644
--- a/system/core/URI.php
+++ b/system/core/URI.php
@@ -628,9 +628,7 @@
 	 */
 	public function ruri_string()
 	{
-		global $RTR;
-
-		return ltrim($RTR->directory, '/').implode('/', $this->rsegments);
+		return ltrim(load_class('Router', 'core')->directory, '/').implode('/', $this->rsegments);
 	}
 
 }