Merge remote-tracking branch 'remotes/ehabkost/tags/x86-pull-request' into staging

Merge remote-tracking branch 'remotes/ehabkost/tags/x86-pull-request' into staging

x86 and memory backends queue, 2016-09-05

This includes a few features that were submitted just after hard
freeze, and a bug fix for memory backend initialization ordering.

# gpg: Signature made Mon 05 Sep 2016 20:50:14 BST
# gpg:                using RSA key 0x2807936F984DC5A6
# gpg: Good signature from "Eduardo Habkost <ehabkost@redhat.com>"
# Primary key fingerprint: 5A32 2FD5 ABC4 D3DB ACCF  D1AA 2807 936F 984D C5A6

* remotes/ehabkost/tags/x86-pull-request:
  vl: Delay initialization of memory backends
  vhost-user-test: Use libqos instead of pxe-virtio.rom
  target-i386: Add more Intel AVX-512 instructions support
  exec: Ensure the only one cpu_index allocation method is used

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