The fetch_docstrings.py script now asks for the Unix '/' separator through graphics.fetch_icon().
This is a final fix for bug 21042 (https://gna.org/bugs/?21042).
The graphics.fetch_icon() function now accepts the 'sep' argument. This defaults to os.sep. But
the docs/latex/fetch_docstrings.py script uses the Unix '/' separator to obtain a LaTeX correct path
on MS Windows.
