Use getdoc(object) instead of object.__doc__ to fix indentation problems.

Use getdoc(object) instead of object.__doc__ to fix indentation problems.
Thanks to Robert Dick <dickrp@ece.northwestern.edu> for reporting this bug
and submitting a patch.

Adjust doc(object) to display useful documentation for plain values (e.g.
help([]) now shows the methods on the list instead of just printing "[]").

(This change has been tested interactively, by generating docs for the
standard library, and by running the module documentation webserver.)