Fix VM memory allocation optimizations by reducing what we allocate on the heap

internal/builtins/close.go

@@ -16,12 +16,12 @@ func Close(args ...object.Object) object.Object {
 		return newError(err.Error())
 	}
 
-	fd := int(args[0].(*object.Integer).Value)
+	fd := int(args[0].(object.Integer).Value)
 
 	err := syscall.Close(fd)
 	if err != nil {
 		return newError("IOError: %s", err)
 	}
 
-	return &object.Null{}
+	return object.Null{}
 }