ppc patch queue 2018-06-18
Next batch of ppc and spapr related patches for the 3.0 release.
* Improved handling of Spectre/Meltdown mitigations for POWER8
* Numerous Mac machine type cleanups and improvements
* Cleanup to cpu realize/unrealize path for spapr
* Create a place for machine-specific per-cpu information, and
start moving some things to it
* Assorted bugfixes