Added Link Layer Discovery Protocol to ethernet.py
Added Link Layer Discovery Protocol to ethernet.py

Applied the patch from http://code.google.com/p/dpkt/issues/detail?id=85

hexcap/dpkt,smutt/dpkt,bpanneton/dpkt,yangbh/dpkt,lkash/test,jack8daniels2/dpkt,jameslittle/dpkt,ashrith/dpkt