[ab] Lisp circle-fill versus native C circle fill

[Luke Crook]

Try running the Lisp circle fill example, (lispbuilder-sdl-examples:circle-3), 
against the C native fill example, (lispbuilder-sdl-gfx-examples:random-
circles).

I get almost 200fps from the Lisp version and almost 600fps from the C version. 
I think that the performance for the Lisp version is pretty good, considering 
the lispbuilder-sdl code is almost completely unoptimized.

- Luke