matplotlib Code

Renamed [xmin, ymin, xmax, ymax] in Bbox to [x0, y0, x1, y1] and
provide functions that really do give xmax etc. as well.
Renamed lbrt to extents and lbwh to bounds (for consistency).
Removed some dead code.

Initial pass of Gtk, Qt, Qt4, Fltk and Wx GUI backends. Lots more
examples passing.

Fix masked array plotting again.

Removing a limits change that shouldn't have been committed.

Forgot to svn add these files in last commit.

Separated path utilities from backend_agg

Bugfix: save colorbar axis label so it won't get lost

Fix bug affecting legend_auto.py

Fix bug in clipping rectangle in PDF

Reduce tendency to use aliased drawing.