+ Wrote ee_draw_triangle() and ee_draw_thin_triangle().
  * libee/box.c:
    + Wrote ee_draw_box(), ee_draw_thin_box() and ee_fill_box().
  * libee/conic.c:
    + Wrote ee_fill_ellipse().
    + First attempt at ee_draw_thin_ellipse(), to be reworked.
  * test/demo.c:
    + Merged demo_lines() and demo_thin_lines().
    + Merged demo_triangles() and demo_outlined_triangles().
    + Wrote demo_box().
    + Use ee_fill_ellipse() in demo_all().