Document SQL injection and authentication bypass in Cacti

Note CVE-2015-8369/upstream bug 0002646: SQL injection in graph.php
was also fixed in this release but that was backported to 0.8.8f and is
covered in a prior entry.

PR: 207444
Security: CVE-2015-8377
Security: CVE-2015-8604
Security: CVE-2016-2313
Security: https://vuxml.FreeBSD.org/freebsd/db3301be-e01c-11e5-b2bd-002590263bf5.html