pcap_io: Remove duplicate const

Arrays are "const pointers" anyway. This fixes a smatch warning.

Make the members of struct pcap_magic_type const as these don't need to
be modified.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
update-oui.py: Adjust OUI matching regular expression

Only match hex digits (not the entire alphabet) and allow for preceeding
whitespaces as this seems to be the new format used.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
configs/oui.conf: Update OUI list

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>