Introduce a handle zapping setting, and enable it by default for release and debug

src/handles.h

Index: src/handles.h
diff --git a/src/handles.h b/src/handles.h
index 140c34e9ba3d096bb538a22dba84e53a2e28b3c0..5dd9fe72acc4974a2d97255584d17ee443b0e05c 100644
--- a/src/handles.h
+++ b/src/handles.h
@@ -177,7 +177,7 @@ class HandleScope {
   // Extend the handle scope making room for more handles.
   static internal::Object** Extend(Isolate* isolate);
 
-#ifdef ENABLE_EXTRA_CHECKS
+#ifdef ENABLE_HANDLE_ZAPPING
   // Zaps the handles in the half-open interval [start, end).
   static void ZapRange(Object** start, Object** end);
 #endif