ModuleProxy doesn't preserve module docstring

[jamadden]

So using deprecatedFrom or deferredFrom, etc, suddenly breaks your Sphinx documentation.

Given foo.py:

"""
This is foo.py
"""
from zope.deferredimport import deprecatedFrom
deprecatedFrom("These live in bar",
               "bar",
               "fizzbin")

You can't get its docstring:

>>> import foo
>>> foo.__doc__
None

This doesn't seem to be a problem in the ProxyBase that ModuleProxy extends:

In [1]: class O(object):
   ...:     """Hi"""
   ...:

In [2]: O.__doc__
Out[2]: 'Hi'

In [3]: O().__doc__
Out[3]: 'Hi'

In [4]: from zope.proxy import ProxyBase

In [5]: proxy = ProxyBase(O)

In [6]: proxy.__doc__
Out[6]: 'Hi'

In [7]: proxy = ProxyBase(O())

In [8]: proxy.__doc__
Out[8]: 'Hi'

(Very vaguely related: zopefoundation/zope.hookable#6)