Replace "operator/*_themes.php" with a controller
Remove "setup_settings_tabs" function
Remove legacy code from csrf_check_token function
Replace "cron.php" with a controller
Replace "index.php" files with a controller.
Remove "check_login" and "force_password" functions
Do not output content in "*Style::render" methods
Remove "start_xml_output" and "start_js_output" functions