Merge remote-tracking branch 'remotes/kraxel/tags/pull-vga-20160411-1' into staging

virtio-gpu: pixman surface fix, block live migration

# gpg: Signature made Mon 11 Apr 2016 11:45:18 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-20160411-1:
  virtio-gpu: block live migration
  ui/virtio-gpu: add and use qemu_create_displaysurface_pixman

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