Made template parser remember last initted page_id and namespace to avoid double init; made additional_headers reassign only do so if $template->additional_headers is empty (it's being blanked somehow, need to come up with a backtrace sometime)

<?php

class Text_Wiki_Render_Plain extends Text_Wiki_Render {
    
    function pre()
    {
        return;
    }
    
    function post()
    {
        return;
    }
    
}
?>