[tor-bugs] #14859 [Onionoo]: Adapt Onionoo's parsing code for MaxMind's GeoLite2 City files to their new format

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#14859: Adapt Onionoo's parsing code for MaxMind's GeoLite2 City files to their new
format
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 Reporter:  karsten  |          Owner:
     Type:  defect   |         Status:  new
 Priority:  normal   |      Milestone:
Component:  Onionoo  |        Version:
 Keywords:           |  Actual Points:
Parent ID:           |         Points:
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 MaxMind has changed their file format for GeoLite2 City database files.
 They split up blocks into IPv4 and IPv6 addresses, and they now support
 different locales.  We need to update our parsing code to read their new
 formats.  At the same time we should drop support for the old format in
 order to remove otherwise dead code.

 I'll post a branch in a minute.  Please review.  I'll hold back on merging
 that branch into master until all mirrors have upgraded to the new
 database.  It's just a matter of fetching the latest database and putting
 `GeoLite2-City-Blocks-IPv4.csv` and `GeoLite2-City-Locations-en.csv` into
 the `geoip/` directory.  iwakeh, please let me know when that's the case.
 It's not that mirrors would break, but they would stop resolving IP
 addresses to locations and ASes.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/14859>
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