Merge remote-tracking branch 'remotes/huth-gitlab/tags/pull-request-2018-10-24' into...

- Disable migration-test with TCG on s390x (since there are known problems)
- Small Makefile improvements
- More modern shell scripting changes (use $() instead of ``)
- Add a configure option to disable AVX2

# gpg: Signature made Wed 24 Oct 2018 08:04:33 BST
# gpg:                using RSA key 2ED9D774FE702DB5
# gpg: Good signature from "Thomas Huth <th.huth@gmx.de>"
# gpg:                 aka "Thomas Huth <thuth@redhat.com>"
# gpg:                 aka "Thomas Huth <huth@tuxfamily.org>"
# gpg:                 aka "Thomas Huth <th.huth@posteo.de>"
# Primary key fingerprint: 27B8 8847 EEE0 2501 18F3  EAB9 2ED9 D774 FE70 2DB5

* remotes/huth-gitlab/tags/pull-request-2018-10-24:
  configure: Provide option to explicitly disable AVX2
  po/Makefile: Modern shell scripting (use $() instead of ``)
  debian-bootstrap.pre: Modern shell scripting (use $() instead of ``)
  configs: Add a CONFIG_SMC37C669 switch for the "smc37c669-superio" device
  hw/core: Move null-machine into the common-obj list
  tests/migration-test: Disable s390x test when running with TCG

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