Making "extracted_ethertype" static to "print-ether.c" broke other

Making "extracted_ethertype" static to "print-ether.c" broke other
dissectors that expected calls to "llc_print()" to set it.  (Thanks and
a tip of the hat to Olaf Kirch <[email protected]> for noticing this.)

Make "ether_encap_print()" and "llc_print()" take a pointer to an
extracted-Ethertype variable as an argument, have "llc_print()" pass it
to "ether_encap_print()", and have "ether_encap_print()" set what it
points to rather than setting a static "extracted_ethertype" variable.

Get rid of said static "extracted_ethertype" variable in favor of one
local to "ether_if_print()", just as other link-layer dissectors have
local "extracted_ethertype" variables.