Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches (rebased Stefan's pull request)

# gpg: Signature made Thu 12 Nov 2015 15:34:16 GMT using RSA key ID C88F2FD6
# gpg: Good signature from "Kevin Wolf <[email protected]>"

* remotes/kevin/tags/for-upstream: (43 commits)
  block: Update copyright of the accounting code
  scsi-disk: Account for failed operations
  macio: Account for failed operations
  ide: Account for failed and invalid operations
  atapi: Account for failed and invalid operations
  xen_disk: Account for failed and invalid operations
  virtio-blk: Account for failed and invalid operations
  nvme: Account for failed and invalid operations
  iotests: Add test for the block device statistics
  block: Use QEMU_CLOCK_VIRTUAL for the accounting code in qtest mode
  qemu-io: Account for failed, invalid and flush operations
  block: New option to define the intervals for collecting I/O statistics
  block: Add average I/O queue depth to BlockDeviceTimedStats
  block: Compute minimum, maximum and average I/O latencies
  block: Allow configuring whether to account failed and invalid ops
  block: Add statistics for failed and invalid I/O operations
  block: Add idle_time_ns to BlockDeviceStats
  util: Infrastructure for computing recent averages
  block: define 'clock_type' for the accounting code
  ide: Account for write operations correctly
  ...

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