Add custom allocator for precise marking and add more tools

* CustomAllocator : Supports precise marking for specified objects.
                    (also supports iteration of specific typed objects)
* HeapVisualizer : Track and visualize heap usage info.
* GCLeakChecker : Shows where the false reference came from.
                  (Developer should specify the location of false reference)
* Add support for incremental build of bdwgc

src/runtime/ArrayObject.cpp

@@ -90,4 +90,15 @@ void ArrayObject::sort(ExecutionState& state, std::function<bool(const Value& a,
     }
     Object::sort(state, comp);
 }
+
+void* ArrayObject::operator new(size_t size)
+{
+    return CustomAllocator<ArrayObject>().allocate(1);
+}
+
+void ArrayObject::iterateArrays(ExecutionState& state, HeapObjectIteratorCallback callback)
+{
+    iterateSpecificKindOfObject(state, HeapObjectKind::ArrayObjectKind, callback);
+}
+
 }