Only return IPv4 addresses if
a non-loopback IPv4 address is configured for the system. Only return IPv6
addresses if a non-loopback IPv6 address is configured for the system.
static const flags address_configured = implementation_defined;
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)