Merge remote-tracking branch 'origin/ds'

Merge remote-tracking branch 'origin/ds'

* origin/ds:
  ds: stop caring about event flags set by epoll/poll/kqueue
  ds: do not distinguish between POLLHUP and POLLERR
  ds: remove read method, here, too
  nntp: use sysread to append to existing buffer
  ds: remove steal_socket method
  ds: remove {fd} field
  ds: reduce Errno imports and drop ->close reason
  ds: cleanup Errno imports and favor constant comparisons
  ds: simplify write buffer accounting