KEA_QUERY4_RAI	hex string of the entire optin 82
KEA_QUERY4_RAI_CIRCUIT_ID hex string of suboption 1
KEA_QUERY4_RAI_REMOTE_ID hex string of suboption 2

Fix #18

The getMAC method of pkt4 seems to retrieve the mac of the packet sender
which is not the client MAC if a dhcp-relay is used.

The getHWAddr seems to be the method used in the KEA server (it's used in
src/bin/dhcp4/dhcp4_srv.cc of the KEA 1.6.1 sources) and return the
expected MAC address.

I test this patch with KEA 1.6.1 sources and hook release v1.3.1, it work
as expected.
Without this path the MAC address in KEA_QUERY4_HWADDR is the MAC address
of my default gateway, because the packet is forwarded from a dhcp-relay.

Removing t1/t2 timers from hook as t1/t2 timers were removed from Kea's Lease struct.

We want to parse both queries and responses, but they have the same type,
so just make the parsing code common.

getMAC() seems to be the generic interface (working for both IPv4 and
IPv6), while getHWAddr() is specific to IPv4.

In addition, getMAC() properly sets the "source" of the MAC address, while
getHWAddr() does not.

I have no idea what they are used for, but some people might find them
useful.

This reverts commit 5d1c2b25.

The segfault was actually caused by a version mismatch between Kea and
this hook, the code should be safe as it was.

This is undocumented in Kea, but lease6_renew and lease6_rebind can get
either a "ia_na" and "ia_pd" parameter.  Handle both to avoid an exception
being raised when "ia_na" is not present.

This makes it clearer that these variables are used for debug.

This avoids variable name conflicts and makes it easier to identify
variables coming from the hook.