* Resynchronise with Debian. Remaining changes: - Write out /etc/crypttab using UUIDs, like we do for /etc/fstab. - Skip loading partman-crypto-loop for now, as we don't support it in Ubuntu. - Disable partition erasing by default, as it's very slow and only of moderate value. - Warn that the passphrase cannot be recovered if lost. - Handle dm_mod and dm_crypt specially in crypto_load_module, to cope with them being built-in.