Process VLAN frames and Alteon jumbo frames in the Ethernet printer.

Process VLAN frames and Alteon jumbo frames in the Ethernet printer.

Instead of having the Ethernet-type handler process the VLAN and Alteon
jumbo frame Ethernet type values, process them in the Ethernet (and
Linux cooked-mode) dissectors.  This makes it easier for the right MAC
addresses to be printed for those packets.

As part of that, rename ether_encap_print() to ethertype_print() - it
doesn't print encapsulated Ethernet frames, it prints payloads whose
packet type is indicated by an Ethernet type field value - and remove
the no-longer-needed "extracted Ethernet type" argument.  That also lets
us eliminate it from the SNAP print routine.

Make ether_print() take a function, and an argument to pass to that
function, as parameters, so that, for example, the ATM LANE printer can
use it and put the LEC ID into the link-layer headeer printout.