Merge branch 'master' of https://github.com/bvanassche/fio

* 'master' of https://github.com/bvanassche/fio:
  t/read-to-pipe-async: Complain if pthread_detach() fails
  t/read-to-pipe-async: Do not divide by zero
  t/memlock: Verify 'threads' argument
  server: Make it explicit that the setsockopt() return value is ignored
  blktrace: Fix memory leaks in error paths
  blktrace: Check value of 'merge_buf' pointer before using it
  blktrace: Pass a positive error code to td_verror()