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

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

Pull request

v2:
 * Drop merge failure from a previous pull request that broke virtio-blk on ARM
   guests
 * Add Parallels XML patch series

# gpg: Signature made Mon 22 Jan 2018 16:00:40 GMT
# gpg:                using RSA key 0x9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <[email protected]>"
# gpg:                 aka "Stefan Hajnoczi <[email protected]>"
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  block/parallels: add backing support to readv/writev
  block/parallels: replace some magic numbers
  block/parallels: move some structures into header
  configure: add dependency
  docs/interop/prl-xml: description of Parallels Disk format
  block: add block_set_io_throttle virtio-blk-pci QMP example

Signed-off-by: Peter Maydell <[email protected]>