LIBGRAPH functions:
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/** GFX_Line(x1,y1, x2,y2, col)
    Draw a line from x1,y1 to x2,y2
    using the Bresenham Algorithm
    top    left  is   0, 0
    bottom right is 127,63
    color: 0 white
           1 black
           2 negate image contents
*/


/** GFX_Area(x1,y1, x2,y2, col)
    Fill rectangular area from x1,y1 to x2,y2
    it must hold: x1<x2 AND y1<y2
    top    left  is   0, 0
    bottom right is 127,63
    color: 0 white
           1 black
           2 negate image contents
*/