Merge remote-tracking branch 'remotes/berrange/tags/pull-qio-2017-01-23-2' into staging

Merge io/ 2017-01-23

# gpg: Signature made Mon 23 Jan 2017 15:56:14 GMT
# gpg:                using RSA key 0xBE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>"
# gpg:                 aka "Daniel P. Berrange <berrange@redhat.com>"
# Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E  8E3F BE86 EBB4 1510 4FDF

* remotes/berrange/tags/pull-qio-2017-01-23-2:
  io: introduce a DNS resolver API
  io: remove Error parameter from QIOTask thread worker
  io: change the QIOTask callback signature
  io: add ability to associate an error with a task
  io: add ability to associate an opaque "result" with with a task
  io: fix typo in docs for QIOTask
  io: stop incrementing reference in qio_task_get_source
  sockets: add ability to disable DNS resolution for InetSocketAddress

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>