As of Piwik 1.3, IP addresses are stored in the DB has VARBINARY(16),
and passed around in network address format which has the advantage of
being in big-endian byte order. This allows for binary-safe string
comparison of addresses (of the same length), even on Intel x86.
As a matter of naming convention, we use $ip for the network address format
and $ipString for the presentation format (i.e., human-readable form).
We're not using the network address format (in_addr) for socket functions,
so we don't have to worry about incompatibility with Windows UNICODE
and inetPtonW().