When for example 'package/net/adblock' and DNSSEC vs NTP robustness
is enabled, significant restart thrashing can occur at boot up. DHCP
lease triggers may be occuring at the same time. Unbounds DNS-DHCP
may be incomplete until new DHCP solicit events. Solve this by
leaving a passive but complete host conf file during lease trigger.

Signed-off-by: Eric Luehrsen <ericluehrsen@hotmail.com>

Bug fix dhcp4_slaac6 option was adding to all IP6 routes.
Filtering was added to this process to only include addresses
served from "this dhcp interface."

adblock 2.3.0 file output is now detected and automatically
integrated into Unbound local-zones. adblock deposites its
block site zone-files into /var/lib/unbound. If this is not
desired, then disable adblock or reconfigure to avoid Unbound.

Signed-off-by: Eric Luehrsen <ericluehrsen@hotmail.com>

The UCI for Unbound already links to dnsmasq, but what
if with Unbound, we want to configure a plain dhcp server.
Most servers can call a script for lease events. That
script can then formulate DNS records and load them
with unbound-control (dependency).

The files added here work with OpenWRT/LEDE odhcpd, such
that it can be run alone. They can be used as examples
for any dhcp server. 'odhcpd.sh' is to be called by
odhcpd when a lease event occurs. 'odhcpd.awk' is called
internal to the shell script. The awk script handles
any tricky reformating that may be required.

/etc/config/dhcp
config odhcpd 'odhcpd'
  option leasetrigger '/usr/lib/unbound/odhcpd.sh'

Signed-off-by: Eric Luehrsen <ericluehrsen@hotmail.com>