according to draft-ietf-ipngwg-icmp-name-lookups-04 to 05 change.
This is necessary before 4.0, because,
-This change is non backword compatible
-Other KAME derived platforms applied 05
-Author of the draft said he never do backword imcompatible changes
again.
Approved by: jkh
Obtained from: KAME project
-Open socket() at first and then setuid() to actual user.
-Allow ping6 preload option only for root.
Approved by: jkh
Submitted by: Neil Blakey-Milner <nbm@mithrandr.moria.org>
(1)added error check of if_nameindex() return value at getaddrinfo().
(2)print out more detailed information when getaddrinfo() error value
is EAI_SYSTEM.(in this case system error num is kept in errno)
(1) is Discovered by: jinmei@kame.net in KAME environment.
