Add missing isa pointer.
This test was accidentally passing sometimes, with the isa pointer being
set using some bit of memory in inter-object padding.  This breaks
horribly with an allocator that packs objects densely.
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
__attribute__((objc_root_class))
-@interface Root @end
+@interface Root
+{
+ id isa;
+}
+@end
@interface DefaultSuperclass: Root @end
// test: new superclass when not initialized at the time of class_setSuperclass
