using base_url in errors/error_404.php

[eluser]CroNiX[/eluser]
It's because when something is missing, it triggers the 404 before the rest of CI is loaded (doesn't need to load everything if it's a missing resource which it checks for at the bottom of CodeIgniter.php), so some basic functions aren't available to the error_404().

I'm not sure if setting a '404_override' (see routes) controller fixes that, but it probably does.