Patch for utmp ut_host.
GNU finger uses ut_host information in utmp.
From src/usr.bin/login/login.c CVS log, after 2.2 source tree,
login.c write numerical address to ut_host.
(1.12 comment of login.c)
So this patch is to translate numerical address to hostname.
Special Thanks to Tung-Hui Hu <hhui@arcfour.com>.
Submitted by: sanpei@yy.cs.keio.ac.jp
(Closing part of #PR 2360.)