Add commented out code for getting size once we know the type

Author: NHDaly

src/gc-heap-snapshot.cpp

@@ -140,7 +140,7 @@ JL_DLLEXPORT void record_node_to_gc_snapshot(jl_value_t *a) {
         "", // string type;
         "", // string name;
         (size_t)a, // size_t id;
-        0, // size_t self_size;
+        /*jl_datatype_size(type)*/ 0, // size_t self_size;
         0, // int edge_count;
         0, // size_t trace_node_id;
         0 // int detachedness;  // 0 - unknown,  1 - attached;  2 - detached