Merge remote-tracking branch 'remotes/kraxel/tags/pull-vga-20150707-1' into staging

virtio-gpu property fixes, add testcase

# gpg: Signature made Tue Jul  7 10:24:16 2015 BST using RSA key ID D3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"

* remotes/kraxel/tags/pull-vga-20150707-1:
  virtio-gpu: add to display-vga test
  virtio-gpu: use virtio_instance_init_common, fixup properties
  virtio-gpu: update console device property.

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