[ ] IPv6: do not forget about 2002:xxyy:zztt::/48, ::a.b.c.d and ::ffff:a.b.c.d.
[ ] endianess checks
[ ] Remove extra pointer from core structure and add a parallel list for 
'extra' to be cache friendly. Do not forget that pointer is 8 bytes on x86_64!
[ ] We can store only first 64 bits of IPv6 addreses?
[ ] We always split in half, so we may store in a table the middle points and
to not compute them every time. But this means more cache misses. :(
[ ] elap_load is in seconds?! Should be in miliseconds!
[ ] UDP
[ ] Dependencies: unzip, gzip, wget
[ ] ip2clue_error is mixed between the threads!
[ ] Extend extra for 'text' parsers (long country etc.).
[ ] Allow client to specify the format.
[ ] Maxmind binary file?
[ ]