Merge remote-tracking branch 'remotes/mst/tags/for_upstream' into staging

vhost, pc: fixes for 2.5

Minor vhost fixes.  HW version tweak for PC.
Documentation and test updates.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

# gpg: Signature made Thu 26 Nov 2015 16:40:25 GMT using RSA key ID D28D5469
# gpg: Good signature from "Michael S. Tsirkin <mst@kernel.org>"
# gpg:                 aka "Michael S. Tsirkin <mst@redhat.com>"

* remotes/mst/tags/for_upstream:
  vhost-user-test: fix migration overlap test
  Fix memory leak on error
  Revert "vhost: send SET_VRING_ENABLE at start/stop"
  tests/vhost-user-bridge: read command line arguments
  tests/vhost-user-bridge: propose GUEST_ANNOUNCE feature
  vhost-user: clarify start and enable
  vhost-user: set link down when the char device is closed
  pc: Don't set hw_version on pc-*-2.5
  osdep: Change default value of qemu_hw_version() to "2.5+"

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