Introduce --zap-cpp-pointers (off by default)

src/api-arguments.h

Index: src/api-arguments.h
diff --git a/src/api-arguments.h b/src/api-arguments.h
index ca7b4833e9947e41b1e3e2009e699e4e88d2b823..992469a49b82fad5b3dae5b7bcee99089abc7fcb 100644
--- a/src/api-arguments.h
+++ b/src/api-arguments.h
@@ -18,7 +18,7 @@ namespace internal {
 template <int kArrayLength>
 class CustomArgumentsBase : public Relocatable {
  public:
-  virtual inline void IterateInstance(RootVisitor* v) {
+  inline void IterateInstance(RootVisitor* v) override {
     v->VisitRootPointers(Root::kRelocatable, values_, values_ + kArrayLength);
   }