Merge remote-tracking branch 'remotes/afaerber/tags/qom-devices-for-2.0' into staging

QOM/QTest infrastructure fixes

* QOM machine memory and build fixes
* QOM link<> and child<> property reference counting fixes

# gpg: Signature made Wed 19 Mar 2014 21:44:04 GMT using RSA key ID 3E7E013F
# gpg: Good signature from "Andreas Färber <afaerber@suse.de>"
# gpg:                 aka "Andreas Färber <afaerber@suse.com>"

* remotes/afaerber/tags/qom-devices-for-2.0:
  virtio-rng: Avoid default_backend refcount leak
  qom: Add check() argument to object_property_add_link()
  qom: Make QOM link property unref optional
  qom: Don't make link NULL on object_property_set_link() failure
  qom: Split object_property_set_link()
  vl.c: Fix OpenBSD compilation issue due to namespace collisions
  vl.c: Fix memory leak in qemu_register_machine()

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