Merge remote-tracking branch 'remotes/ehabkost/tags/x86-for-3.1-pull-request' into staging

pc-*-3.1 machine-types

# gpg: Signature made Tue 20 Nov 2018 13:43:24 GMT
# gpg:                using RSA key 2807936F984DC5A6
# 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-for-3.1-pull-request:
  hw/i386: add pc-i440fx-3.1 & pc-q35-3.1

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