* Renamed cucul_*_canvas_frame() to cucul_*_frame() because we bloody well
    know that a frame belongs to a canvas.

of toilet needs it.

* More debugging information in the import/export and font functions.

cucul_export_file() but I'm not sure yet this is a good idea.
  * Use the new import/export API in libcaca.

cucul_import_file().

documentation errors or imprecisions.

a file and a memory area into a libcucul buffer.
  * Changed the cucul_import_canvas() prototype so that it uses libcucul
    buffers instead of simple memory areas.

* Started changing function prototypes so that they return an integer
    instead of void, just in case they might fail.

in all .c files that needed it.

their name, eg. cucul_create() -> cucul_create_canvas() etc.
  * Moved buffer-related functions to cucul/buffer.c.