into addresses as we have no idea what address family they belong to.
When -n is not specified, resolve IPv6 as well as IPv4 addresses found
in the host field of utmp. Use realhostname_sa() to resolve addresses
(the old code was wrong).
Rename ``x'' to ``x_suffix'' to avoid confusion.
Hard code the host column width to 16 (against the imminent increase
of UT_HOSTSIZE in utmp.h).