Canvas "2.0"

[AgentD]

• Replace X11 canvas implementations with MIT-SHM based canvas
  • If MIT-SHM is available, use mem_canvas with SHM-XImage or SHM-Pixmap
  • If XRender is available, user existing XRender pixmaps with XRender compositing
  • If XRender is not available, let the mem_canvas do everything
  • If MIT-SHM is not available, use normal mem_canvas and transfer to pixmap via XImage
• Make line drawing functon generic
  • Current linedrawing function can draw either horizontally or vertically
  • Add generic bresenham or xiaolin wu based solution
• Add more drawing and filling functions
  • Triangles(?)
  • Elipses(?)
  • Round rects(?)
• Add documentation chapters and sample code

[AgentD]

Removed from milestone. Still needs clarification:

• SGUI tries to be small and minimalistic.
• Do we really need most of that?
• Wouldn't some of this be out of scope?