Calculate stateless IPv6 address

In order to support stateless IPv6, neutron should calculate IPv6 address base
on IPv6 prefix and MAC address via EUI-64 specification.  This change adds
common library to calculate IPv6 address.

Partially-implements bp ipv6-two-attributes
Co-Authored-By: Xu Han Peng <xuhanp@cn.ibm.com>

Change-Id: I68ccbc42388ec760d6fead242e080822ca753913
Merge "Calculate stateless IPv6 address"