Graphic primitives, rotozoomer, framerate control and image filters

The SDL_gfx library offers several components: Graphic Primitives,
Rotozoomer, Framerate control, and MMX image filters. The Primitives
component provides basic drawing routines: pixels, hlines, vlines, lines,
aa-lines, rectangles, circles, ellipses, trigons, polygons, Bezier curves,
and an 8x8 pixmap font for drawing onto any SDL Surface. Full alpha
blending, hardware surface locking, and all surface depths are supported.
The Rotozoomer can use interpolation for high quality output.