CVE-2016-7985,7986/Change the way protocols print link-layer addresses.

CVE-2016-7985,7986/Change the way protocols print link-layer addresses.

If a protocol that runs under a link-layer protocol would print the
link-layer addresses for the packet as source and destination addresses
for the packet, don't have it blithely assume those link-layer addresses
are present or are at a particular offset from the beginning of that
protocol's data; Ethertypes, for example, are used by a number of
protocols, not all of which have Ethernet headers and not all of which
have any MAC headers.

Instead, pass the printers for those protocols structures with a pointer
to the address data and a pointer to a routine that prints the address.

Fixes some heap overflows found with American Fuzzy Lop by Hanno Böck.