GeoIP Upgrade: Use legacy codes for missing regions

Follow-up of #900

The old regions codes can be found for instance on:
http://fr.openclassrooms.com/forum/sujet/table-pour-les-codes-region-15280#.U3nRaliSyjQ

There you find for instance the old GeoLite code GB17 for Greater London, which is missing in the [regions listing](http://geolite.maxmind.com/download/geoip/misc/region_codes.csv) because it still has no code in ISO 3166-2 and FIPS 10-4.