package/dovecot: bump version to 2.3.9.2
Release notes:
https://dovecot.org/pipermail/dovecot-news/2019-October/000419.html
https://dovecot.org/pipermail/dovecot-news/2019-December/000423.html
https://dovecot.org/pipermail/dovecot-news/2019-December/000425.html
https://dovecot.org/pipermail/dovecot-news/2019-December/000427.html
Please note that according to
https://security-tracker.debian.org/tracker/CVE-2019-19722
CVE-2019-19722 fixes a bug introduced in 2.3.9 so backporting this patch
to older buildroot branches is not necessary.
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>