Fixes #612595.

    revision 1.6 of turtle.py

Patch #536117: Typo in turtle.py.
2.2.2 candidate.

Python's logolike module turtle.py did not display
the turtle except when actually drawing lines.
This patch changes the turtle.py module so that
it displays the turtle at all times when tracing is
on. This is similar to the the way that logo works.
When tracing is off the turtle will not be displayed.

than a pixel don't get drawn at all. If you're building long curves
made of such lines, this is a bad thing.

Subclass Error from Exception.

Different action on WM_DELETE_WINDOW is more likely to do the right thing,
allowing us to destroy old windows.

using Canvas coordinates, and goto() uses turtle coordinates
and accepts variable argument lists.