Updated version number to v2.2.UNSTABLE and added a warning to configure.
Updated version number to v2.2.UNSTABLE and added a warning to configure.

jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot