Make dir() wordier (see the new docstring). The new behavior is a mixed

bag.  It's clearly wrong for classic classes, at heart because a classic
class doesn't have a __class__ attribute, and I'm unclear on whether
that's feature or bug.  I'll repair this once I find out (in the
meantime, dir() applied to classic classes won't find the base classes,
while dir() applied to a classic-class instance *will* find the base
classes but not *their* base classes).

Please give the new dir() a try and see whether you love it or hate it.
The new dir([]) behavior is something I could come to love.  Here's
something to hate:

>>> class C:
...     pass
...
>>> c = C()
>>> dir(c)
['__doc__', '__module__']
>>>

The idea that an instance has a __doc__ attribute is jarring (of course
it's really c.__class__.__doc__ == C.__doc__; likewise for __module__).

OTOH, the code already has too many special cases, and dir(x) doesn't
have a compelling or clear purpose when x isn't a module.

Lib/test/test_generators.py

@@ -383,14 +383,8 @@ From the Iterators list, about the types of these things.
 >>> i = g()
 >>> type(i)
 <type 'generator'>
-
-XXX dir(object) *generally* doesn't return useful stuff in descr-branch.
->>> dir(i)
-[]
-
-Was hoping to see this instead:
+>>> [s for s in dir(i) if not s.startswith('_')]
 ['gi_frame', 'gi_running', 'next']
-
 >>> print i.next.__doc__
 x.next() -> the next value, or raise StopIteration
 >>> iter(i) is i