I had previously assumed that if AF_INET6 is defined, IPv6 support was
present. Some psychopathic console SDKs which shall not be named
actually define AF_INET6 but none of the IPv6 structures. As there is
therefore no way to determine whether IPv6 support is present at
preprocessor time, I'm ust assuming that HAVE_SOCKET_LEGACY implies no
IPv6. This means in effect that no consoles get IPv6 support.
Silence some Coverity warnings (including a real memory leak) and be
more careful about checking IPv6 mode (for backwards compatibility with
systems that don't support IPv6 but may run code compiled to expect IPv6)