inclusion of these names was unintentional and in most cases is a namespace violation. Daniel Sabogal tracked down and reported these.
the getifaddrs interface seems to have been invented by glibc, and they expose socket.h, so for us not to do so is just gratuitous incompatibility with the interface we're mimicing.
supports ipv4 and ipv6, but not the "extended" usage where usage statistics and other info are assigned to ifa_data members of duplicate entries with AF_PACKET family.