3581 IPv6 support

I think this resolves #3581.
- updated geoip api from https://github.com/maxmind/geoip-api-php v1.14
- updated GeoIP/Php.php (and LocationProvider.php)
- added a test

Am I correct to see that only the GeoIp\Php class needs modification? GeoIP\Pecl still doesn't seem to work with IPv6 and GeoIP\ServerBased seems to handle IPv6 already?

Running `console tests:run --file tests/PHPUnit/System/ManyVisitorsOneWebsiteTest.php` fails on some assertions (not mine). For now, I kept those as they are.
Not directly.
GeoIP->getIpFromInfo() returns a string.

Also, it returns an IPv4 address when the original address is IPv4 mapped to IPv6. The code already worked like that and I thought it best to keep it that way. Added benefit is that visits from either IPv4 or IPv4-mapped-to-IPv6 addres are counted as comming from one address.