Document Drupal vulnerabilities

PR: 214813
Security: CVE-2016-9449
Security: CVE-2016-9450
Security: CVE-2016-9451
Security: CVE-2016-9452
Security: https://vuxml.freebsd.org/freebsd/8db24888-b2f5-11e6-8153-00248c0c745d.html

Approved by: mentors (implicit)