do not hardcode if_mtu values in here, except for IFT_{ARC,FDDI} - they need special handling.  makes it possible to take advantage of 9k ether frames.
do not hardcode if_mtu values in here, except for IFT_{ARC,FDDI} -
they need special handling.  makes it possible to take advantage of 9k ether
frames.

Obtained from:	NetBSD

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase