Merge branch 'lsfd-tcp6' of https://github.com/masatake/util-linux

* 'lsfd-tcp6' of https://github.com/masatake/util-linux:
  lsfd: use PRIu16 instead of SCNu16 in xasprintf
  lsfd: specify variables instead of types in sizeof operator
  lsfd: (test) add a case for TCPv6 sockets
  tests: (mkfds) add tcp6 factory
  lsfd: (man) write about TCP6 related columns
  lsfd: use extra information loaded from /proc/net/tcp6
  lsfd: (man) fix typos