* documentation (based on python bindings)
   * Ethumb
   * Ethumb_Client

 * memory handling:
   * zero pointer parameters before failing on SAFETY macros (file_get, etc)
   * Ethumb_Client:
      * call free_data() on clear() and queue_remove()
      * check other places to ensure free_data() on requests.
   * disconnect() should cancel everything, regardless of being connected
   * disconnect() cannot call clear() as it is asynchronous (maybe block?)
   * disconnect() should cancel all clear_pending

 * callback:
   * const void *data on function registration, cast when call.
   * give generated_cb the Ethumb_Client parameter.

 * unit tests, be them in C or Python, covering:
   * thumbnail generation respect parameters (size, format...)
   * respect fdo standards (hash, location, etc, uri with spaces...)
   * server died recovery, just add timeout and kill server before expires

 * examples:
   * simple client example in C, see 01-simple.py
   * error handling, including reconnection.