Merge remote-tracking branch 'remotes/sstabellini/tags/xen-2015-12-22' into staging

Merge remote-tracking branch 'remotes/sstabellini/tags/xen-2015-12-22' into staging

Xen 2015/12/22

# gpg: Signature made Tue 22 Dec 2015 16:17:57 GMT using RSA key ID 70E1AE90
# gpg: Good signature from "Stefano Stabellini <stefano.stabellini@eu.citrix.com>"

* remotes/sstabellini/tags/xen-2015-12-22:
  xen_disk: treat "vhd" as "vpc"
  xen/pass-through: correctly deal with RW1C bits
  xen/MSI-X: really enforce alignment
  xen/MSI-X: latch MSI-X table writes

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