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

Block patches for 2.3.0-rc1

# gpg: Signature made Thu Mar 19 15:03:26 2015 GMT using RSA key ID C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"

* remotes/kevin/tags/for-upstream:
  block: Fix blockdev-backup not to use funky error class
  raw-posix: Deprecate aio=threads fallback without O_DIRECT
  raw-posix: Deprecate host floppy passthrough

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