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

target-i386: finally enable "check" mode by default

# gpg: Signature made Wed 28 Oct 2015 14:13:10 GMT using RSA key ID 984DC5A6
# gpg: Good signature from "Eduardo Habkost <ehabkost@redhat.com>"

* remotes/ehabkost/tags/x86-pull-request:
  target-i386: Enable "check" mode by default
  target-i386: Don't left shift negative constant

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