Security fix, CVE-2017-14494, Infoleak handling DHCPv6 forwarded requests.
Fix information leak in DHCPv6. A crafted DHCPv6 packet can
cause dnsmasq to forward memory from outside the packet
buffer to a DHCPv6 server when acting as a relay.
Signed-off-by: Petr Menšík <pemensik@redhat.com>