Replace external dependancy of Imaging with Pillow.

[ken@…]

This is for asymptote, but I'm not putting that in the summary in case a new version of asy gets released before I address this.

Asymptote includes xasy which is a minimal gui, sort of documented at ​http://asymptote.sourceforge.net/doc/GUI-usage.html#GUI-usage - it needs the PIL/ImageTk and PIL/Image modules, the link to Imaging is old and not at PyPi.

While looking at my python modules I discovered that PIL was a very old-style module (the Imaging link might be to a subset of it) and there is a current, maintained, fork called Pillow ​https://pypi.python.org/pypi/Pillow/

I've now tried that in a fresh install on a system where Imaging had not been installed, it works the same and does not need a patch.

I still don't think xasy is useful, but it runs and lets me e.g. add text and save.

[ken@…]

r19324.