Merge branch 'lsfd-sock-unix-xinfo' of https://github.com/masatake/util-linux

Merge branch 'lsfd-sock-unix-xinfo' of https://github.com/masatake/util-linux

* 'lsfd-sock-unix-xinfo' of https://github.com/masatake/util-linux:
  tests: (lsfd) add a case for testing SOCKNETNS column
  tests: (lsfd) extend unix-stream test case to test SEQPACKET socket
  tests: (lsfd) add a case testing UNIX+DGRAM socket
  tests: (lsfd) add a case testing UNIX-STREAM sockets
  tests: (mkfds) add a factory making unix sockets
  lsfd: (man) write about UNIX-STREAM and UNIX sockets
  lsfd: use extra information loaded from /proc/net/unix
  lsfd: add new columns: SOCKNETNS, SOCKSTATE, and SOCKTYPE as stubs
  lsfd: facilitate the way to attach extra info loaded from /proc/net/* to sockets
  tests: (mkfds) quit when a byte is given via standard input
  tests: (mkfds) call close method of factory only when it is specified
  tests: (mkfds) cosmetic change, deleting empty lines
  tests: (mkfds) add boolean, a new parameter type
  tests: (mkfds) add a method for printing factory specific data to struct factory
  tests: (mkfds) allow a factory to make a factory specific temporarily data
  tests: (mkfds) delete unused "child" parameter for factories
  tests: (mkfds) delete per-factory "fork" field