Remove vestiges of Qt's own sockaddr_in6 and sockaddr_storage

Remove vestiges of Qt's own sockaddr_in6 and sockaddr_storage

We weren't using qt_sockaddr_storage, so it's not a problem. But since
we're not using it anyway, we don't really need it. The storage is only
needed if we needed to get a bigger socket address and that only happens
with Unix sockets (paths).

sockaddr_in6, however, was just wrong. Some systems derived from BSD,
like OS X, have a sXX_len field containing the length of the socket
address structure and our qt_sockaddr_in6 was missing sin6_len. As a
result, setting sin6_family was just plain wrong on little-endian
systems. Like all modern systems running BSDs and OS X...

Change-Id: I7de033f80b0e4431b7f1ffff13f900f004c55443
Reviewed-by: Richard J. Moore <rich@kde.org>