from some systems.

cucul_import_canvas().
  * Renamed cucul_create_export() into cucul_export_canvas() for consistency.

now x/y/width/height instead of x1/y1/x2/y2. Avoids unnecessary +1/-1
    computations.

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

* Renamed canvas handle variables from "c" to "cv". Eh ouais mon gros.

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

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.

can add new exporters without changing the API.

* Changed the line, box, ellipsis etc. prototypes so that they use an UTF-8
    string instead of a single character as their last argument.

canvas size (use cucul_init(0, 0) for the old behaviour).