LLDP: Dissector for Hytec specific extensions added

It provides dissection of objects with additional neighbor and link information
defined by Hytec (pcap example available on wiki.wireshark.org/HYTEC).
Also OUI of "Hytec Geraetebau GmbH" added.

Change-Id: I92119e46fd5f4c4b385ac3df3170a4766fe056b7
Reviewed-on: https://code.wireshark.org/review/5107
Petri-Dish: Michael Mann <mmann78@netscape.net>
Reviewed-by: Michael Mann <mmann78@netscape.net>