webcore: Clean up rare codepath
pxpcap: Fix PCapParser

The state machine wasn't going back to the header state after
each packet.  Now it does.
boot: Fix cmdline values with hyphens

The argument processing was doing hypen-to-underscore on both
the left and right side of the equal sign.  Should only do it
on the left side.  Fixed.
packet: Fixes to DHCP options

There were a number of minor bugs here which entirely broke
a couple things.  Fixed now.

* DHCPSecondsOptionBase was parsed slightly wrong
* DHCPOptionOverloadOption's pack function was broken
* Option overload parsing was broken
packet: Fix DNS packing

There was a bug in DNS record packing.
packet: Improved dump() for raw packets
packet: Reintroduce 802.2 LLC/SNAP

I don't think 802.2 worked in any released version of POX (and
maybe not even any released NOX), and the llc file was removed
long ago.  This is a total rewrite and should more or less work.

Additionally, VLAN-in-VLAN is now supported, and the
effective_ethertype should now be more consistent, even though
it should really be called inner_ethertype... and for that
matter, when it's LLC, it's not even necessarily an ethertype,
but whatever.