apply security fixes from Debian and run tests
- apply Debian patch to fix CVE-2021-42260 (rhbz#2253716, rhbz#2253718)
- apply Debian patch to fix CVE-2023-34194 and its duplicate, CVE-2023-40462
(rhbz#2254376, rhbz#2254381)
- fix incorrect text element encoding (upstream isssue #51)
- compile and run tests