if_nameindex with 2.2 kernel

[Roland McGrath]

What is the reason for preferring AF_UNIX over AF_INET at all?  An AF_UNIX
socket can do SIOCGIFCONF but none of the other SIOCGIF* calls that are
needed for e.g. getifaddrs or the existing _res_hconf_reorder_addrs
(SIOCGIFNETMASK)--you must use an AF_INET socket for those to work.  So in
my tree I have made it try AF_INET first unconditionally, so my getifaddrs
implementation can work (and I noticed along the way that the reorder
option in /etc/host.conf can't possibly be working without that change).