MFC 281734-281736,287997-287998:

MFC 281734-281736,287997-287998:

- Fix a crash on a rpc entry when an IPv6 address is explicitly
  specified in -a flag.

- Fix a bug that sockaddr_in was used where sockaddr_in6 should have
  been used.  This was not actually harmful because offsetof(struct
  sockaddr_in, sin_port) is equal to offsetof(struct sockaddr_in6,
  sin6_port).

- Remove unused union p_un.

- Use NI_MAXHOST-long buffer for getnameinfo().
  Although INET6_ADDRSTRLEN was designed to hold the longest
  IPv6 address in IPv4-mapped address format a long time ago,
  getnameinfo() can return scope identifier in addition to it.

git-svn-id: svn://svn.freebsd.org/base/stable/10@288048 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f