POLICY_BUF_LEN should be longer
Now that we can have, and need to write, IPv6 policy items, we need to increase the length of POLICY_BUF_LEN, since the longest possible exit policy item is now "accept6 [ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff]/128:65535-65535\n".
Fortunately, we use POLICY_BUF_LEN in only a few places, none of which make this super harmful, but it could prevent us from formatting some log messages correctly.