Updates pdns-recursor to latest release in the 4.2 series.
Includes backported fixes for CVE-2020-10995, CVE-2020-12244 and
CVE-2020-10030, plus avoid a crash when loading an invalid RPZ.
Full change log for this release is available at:
https://doc.powerdns.com/recursor/changelog/4.2.html#change-4.2.2
Signed-off-by: James Taylor <james@jtaylor.id.au>