Use placement new for ZoneLists in the parser.

src/zone.h

Index: src/zone.h
diff --git a/src/zone.h b/src/zone.h
index 94a6241278d8f0095f5352d240e86e746acc80d6..0aa288179b6ee31a7f8a1f0982c0db030a77c347 100644
--- a/src/zone.h
+++ b/src/zone.h
@@ -178,6 +178,9 @@ class ZoneListAllocationPolicy {
 template<typename T>
 class ZoneList: public List<T, ZoneListAllocationPolicy> {
  public:
+  inline void* operator new(size_t size);
+  inline void* operator new(size_t size, Zone* zone);
+
   // Construct a new ZoneList with the given capacity; the length is
   // always zero. The capacity must be non-negative.
   explicit ZoneList(int capacity)