QOM CPUState refactorings / X86CPU

* TLB invalidation optimizations
* X86CPU initialization cleanups
* Preparations for X86CPU hot-unplug

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* afaerber/tags/qom-cpu-for-anthony:
  target-i386: Cleanup 'foo=val' feature handling
  target-i386: Cleanup 'foo' feature handling
  target-i386: Convert 'check' and 'enforce' to static properties
  target-i386: Convert 'hv_spinlocks' to static property
  target-i386: Convert 'hv_vapic' to static property
  target-i386: Convert 'hv_relaxed' to static property
  cpu-exec: Optimize X86CPU usage in cpu_exec()
  target-i386: Move apic_state field from CPUX86State to X86CPU
  cputlb: Tidy memset() of arrays
  cputlb: Use memset() when flushing entries