For a dynamically constructed type object, fill in the tp_doc slot with
a copy of the argument dict's "__doc__" value, provided the latter exists
and is a string.
NOTE: I don't know what to do if it's a Unicode string, so in that case
tp_doc is left NULL (which shows up as Py_None if you do Class.__doc__).
Note that tp_doc holds a char*, not a general PyObject*.
Taught doctest about static methods, class methods, and property docstrings
in new-style classes. As for inspect.py/pydoc.py before it, the new stuff
needed didn't really fit into the old architecture (but was less of a
strain to force-fit here).
New-style class docstrings still aren't found, but that's the subject
of a different bug and I want to fix that right instead of hacking around
it in doctest.
Tim Peters