matplotlib Code

Add comment about how nan-removal on curves works.

Remove extraneous "public:"

Speed up nan-handling on curves. Add test case for this.

Fix shortening end of path bug in simplifier. Speed up clipper by not using a queue.

Create path_cleanup code for use by the Mac OS-X backend. Refactor C++ code to follow Numpy's guidelines for linking multiple C files into a single extension. Remove dependency of Agg backend on _image.cpp and _ft2font.cpp (simplifies linking problems and reduces generated code size).

Rework the nan-handling/clipping/quantizing/simplification
framework so each is an independent part of a pipeline.
Expose the C++-implementation of all of this so it can be
used from all Python backends. Add rcParam
"path.simplify_threshold" to control the threshold of
similarity below which vertices will be removed.