Minor typo in documentation

[Chris Davies]

Typos on http://www.varnish-cache.org/docs/trunk/tutorial/purging.html#bans

This probably comes from the sphinx markup

sub vcl_recv {
        if (req.request == "BAN") {
                # Same ACL check as above:
                if (!client.ip ~ purge) {
                        error 405 "Not allowed.";
                }
#                ban("req.http.host == " req.http.host
#                      "&& req.url == " req.url);
                ban("req.http.host == " + req.http.host +
                      "&& req.url == " + req.url);

                # Throw a synthetic page so the
                # request won't go to the backend.
#                error 200 "Ban added"
                error 200 "Ban added";

        }
}

missing + for concatenation in ban, missing ; at end of line for error 200