Document earlier dhcpcd security issue that has been fixed in an earlier
version before the security implications were reported.

PR: 208840
Submitted by: Ben Woods <woodsb02@gmail.com>
Submitted by: Roy Marples <roy@marples.name>
Security: CVE-2014-7912
Security: https://vuxml.FreeBSD.org/freebsd/092156c9-04d7-11e6-b1ce-002590263bf5.html