cucul.c just in case.

list of available formats. Also added a few truecolor blocks to the test.

* Added cucul_set_truecolor() for non-ANSI colours.
  * Added new argb32 -> rgb12 conversion functions.

such as cucul_dither_t instead of struct cucul_dither.
  * Made cucul_buffer_t an opaque structure and implemented the two getters
    cucul_get_buffer_data() and cucul_get_buffer_size().
  * Documented all missing functions and function parameters.

hyperlinks! Also, set compact LaTeX mode and a few other Doxygen options.

remove redundencies in the Doxygen documentation.

secure against broken files, but it probably needs peer review.

* Fixed font selection through cucul_font_load().
  * Added a bigger 10x19 bold font.

so that the font can be easily rebuilt.

* Removed ugly hooks from test/font.c.

* Documented most font functions.
  * Cleaned up cucul_render_canvas() and made it actually usable by external
    programs. Removed ugly printf() debug calls.

* Replaced the 8-bit internal font with a 4-bit one.

fg/bg value into its separate argb 4-bit fields.

for the moment.