fix for security issue with python-21.el/python.el

[Dave Love]

I got a second-hand report of a security problem with the way the
inferior interpreter works in my Python mode.  There are patches to work
around it below for python-21.el (for Emacs 21) and python.el (for Emacs
22) as well as one which will apply against the forked mode from Emacs
22, although I wouldn't recommend using that version.

There's an explanation in the commentary added by the patch.  I assume,
but don't know, that this is also appropriate for other systems like MS
Windows.  I've only checked on GNU/Linux, and the Python documentation
says the module-loading behaviour is system-dependent.

The current versions of the mode are under
<URL:http://www.loveshack.ukfsn.org/emacs/>.

python-21.el.diff
Description: python-21.el patch

python.el.diff
Description: python.el (author-maintained) patch

python-emacs.el.diff
Description: python.el (from Emacs 22) patch