Here is a patch that shold fix the deldict bug.  It also
removes the new condition for metaclasses, because it
isn't needed anymore, and fixes bug #1174712.  These two
changes were needed so that the patch could be properly
tested.

The patch does what Armin suggested; the __dict__ descriptor
looks for a builtin base with tp_dictoffset != 0, and if one
is found, it delegates to that base's __dict__ descriptor.

File Added: modify_dict_bug.diff