key patch update

[Daniel J S. <dan...@ie...>]

I updated the key patch and demo.  The demo is in PDF format at

http://acer-access.com/~ds...@ac.../gnuplot/key.pdf

The layout of the plot could use small changes here or there, but this 
should be a good first step toward cleanup.  I'll let it sit for a few 
months to see what people think.

Dan