Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Block pull request

# gpg: Signature made Tue 01 Jul 2014 09:47:15 BST using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"

* remotes/stefanha/tags/block-pull-request: (23 commits)
  block: add backing-file option to block-stream
  block: extend block-commit to accept a string for the backing file
  block: add helper function to determine if a BDS is in a chain
  block: add QAPI command to allow live backing file change
  qapi: Change back sector-count to sectors-count in quorum QAPI events.
  block/cow: Avoid use of uninitialized cow_bs in error path
  block: simplify bdrv_find_base() and bdrv_find_overlay()
  block: make 'top' argument to block-commit optional
  iotests: Add more tests to quick group
  iotests: Add qemu tests to quick group
  iotests: Simplify qemu-iotests-quick.sh
  qemu-img create: add 'nocow' option
  virtio-blk: remove need for explicit x-data-plane=on option
  qdev: drop iothread property type
  virtio-blk: replace x-iothread with iothread link property
  virtio-blk: move qdev properties into virtio-blk.c
  virtio: fix virtio-blk child refcount in transports
  virtio-blk: drop virtio_blk_set_conf()
  virtio-blk: use aliases instead of duplicate qdev properties
  qdev: add qdev_alias_all_properties()
  ...

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

diff --cc hw/core/qdev.c
Simple merge