matplotlib Code

Recommitting my changes to clabel to allow for manual labeling after fixing
problems with indexing identified by Eric Firing on 19 July 2008.

In addition, I have made the following changes:

1) Placed more comments in contour.py with the intention of eventually doing
a rewrite or restructuring of that code.

2) Added two pylab_examples: contour_label_demo.py that tests out some of the
more advanced things that can now be done with contour labeling, and
ginput_manual_clabel.py that demonstrates some uses of ginput,
waitforbuttonpress, and clabel(...,manual=True). The first of these has been
integrated into backend_driver.py, but the second cannot be because it
requires interaction.

Added Gael's backend fallback patch

Expanded delete_masked_points to handle more types of argument

Moved and modified axes_unit.py to cbook_unit.py.
At present it is only testing delete_masked_points,
which was moved from axes to cbook.

In collections draw methods, use get_facecolor and get_edgecolor.
The logic for edgecolors='face' is moved into get_edgecolor so
that it will return the color(s) that will actually be used.
Using the getters means that a derived class can override
them to add more logic to the choice of colors.

Move delete_masked_points() from axes.py to cbook.py so that it's available to more places.

Reverting clabel-related change in contour.py to 5689.
contour_demo.py was broken.

Add a new f2py example that uses F90 (it's still very simple).

Check for nan and inf in axes.delete_masked_points().

restored gtk quit on window close