boost asio from_string rejects valid ipv6 address

[mark andrews <mandrews58@…>]

from RFC 4291 2.2.2, '::2:3:4:5:6:7:8' is a valid ipv6 address
following code incorrectly sets ec.m_val to 10022

std::string thost("::2:3:4:5:6:7:8");
boost::system::error_code ec;
addr = boost::asio::ip::address::from_string(thost, ec);