Addressing some observations made while reviewing other patches. I'm
including the last patch here despite it largely duplicating one that
Jürgen did submit - there's one extra adjustment plus an open question
there.

1: perfc: conditionalize credit/credit2 counters
2: x86/perfc: conditionalize HVM and shadow counters
3: VMX: sync VM-exit perf counters with known VM-exit reasons
4: SVM: sync VM-exit perf counters with known VM-exit reasons
5: xenperf: name "newer" hypercalls

Jan