Merge remote-tracking branch 'remotes/huth/tags/pull-request-2018-02-14' into staging

Various improvements to the qtest checks:
- Clean-ups by Eric Blake with regards to the global_qtest variable
- Some more test cases for the boot-serial tester
- Re-activation of the m48t59-test

# gpg: Signature made Wed 14 Feb 2018 11:07:44 GMT
# 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/tags/pull-request-2018-02-14:
  tests/m48t59: Use the m48t59 test on ppc, too
  tests/Makefile: Derive check-qtest-ppc64-y from check-qtest-ppc-y
  tests/m48t59: Make the test independent of global_qtest
  tests/m48t59: Fix and re-enable the test for sparc
  tests/boot-serial-test: Add support for the aarch64 virt machine
  tests/boot-serial: Add tests for PowerPC Mac machines
  tests/boot-serial: Enable the boot-serial test on SPARC machines, too
  wdt_ib700-test: Drop dependence on global_qtest
  tests/boot-sector: Drop dependence on global_qtest
  qmp-test: Drop dependence on global_qtest
  libqos: Use explicit QTestState for remaining libqos operations
  libqos: Use explicit QTestState for ahci operations
  libqos: Use explicit QTestState for i2c operations
  libqos: Use explicit QTestState for rtas operations
  libqos: Use explicit QTestState for fw_cfg operations
  libqos: Track QTestState with QPCIBus
  libqtest: Use qemu_strtoul()
  tests: Clean up wait for event

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