Code tidy up: reduce the number of global variables.

Add support for win32 link-layer send and receive.

Find portable function to get interface MAC address.

Investigate response packets >60 bytes long, e.g. Windows 2003 Server and
some Cisco.

Add XML or JSON output format.

MPLS tag support.

Add support for Cisco ISL VLANs in addition to 802.1Q VLANs. Suggested by
Daniel at commonexploits.

Modify the IEEE MAC/Vendor mapping code and scripts to cater for the
OUI registry restructuring detailed in:
http://tools.ietf.org/html/draft-ieee-rac-oui-restructuring-01
