Update from 0.7.21 to 0.7.22.

<ChangeLog>

*) Feature: the "none" parameter in the "smtp_auth" directive.

Thanks to Maxim Dounin.

*) Feature: the "$cookie_..." variables.

*) Bugfix: the "directio" directive did not work in XFS filesystem.

*) Bugfix: the resolver did not understand big DNS responses.

Thanks to Zyb.

</ChangeLog>