manuf: Add back the special case for all zeroes

These words from Jörg Mayer are as true today as they were
21 years ago in 49a2f32336,
"I still have yet to see a case when a MAC address starting
with 0:0:0 actually means Xerox", but there are lots of cases
where all zero OUIs, MAC-48s, EUI-64s, etc are used to mean
null.

[skip ci]

tools/make-manuf.py

@@ -230,7 +230,7 @@ def main():
         'OUI36': { 'url': ["https://standards-oui.ieee.org/oui36/", "oui36.csv"], 'min_entries': 1000 },
     }
     oui_d = {
-        MA_L: {},
+        MA_L: { '00:00:00' : ['00:00:00', 'Officially Xerox, but 0:0:0:0:0:0 is more common'] },
         MA_M: {},
         MA_S: {},
     }