Add various older CVEs to the security section
See https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=gstreamer . At least the following are missing:
- CVE-2020-6095
- CVE-2019-9928
- CVE-2017-*
- all older except for CVE-2016-9634 CVE-2016-9635 CVE-2016-9636 CVE-2016-9807 CVE-2016-9445 CVE-2016-9446