NDOize ATM, MPTCP, NTP, VTP & Whiteboard decoders
NDOize 7 more small decoders

This change converts DVMRP, DLT_ENC, EGP, GeoNet, NetFlow, SLIP and TFTP
decoders.
NDOize VRRP decoder
remove duplicate prototypes from netdissect.h
use ND_PRINT in print-esp.c