Clean the request variables - add html entities to GET and slashes if magic_quotes_gpc is Off.
What it does:
- cleans the request variables (ENV, GET, POST, COOKIE, SERVER) and
- makes sure the query string was parsed correctly.
- handles the URLs passed by the queryless URLs option.
- makes sure, regardless of php.ini, everything has slashes.
- sets up $board, $topic, and $scripturl and $_REQUEST['start'].
- determines, or rather tries to determine, the client's IP.