the curl_multi_handle_control() idea

   internally use and assume the multi interface. The select()-loop should use

   curl_multi_socket().

 * curl_multi_handle_control() - this can control the easy handle (while)

   added to a multi handle in various ways:

   o RESTART, unconditionally restart this easy handle's transfer from the

     start, re-init the state

   o RESTART_COMPLETED, restart this easy handle's transfer but only if the

     existing transfer has already completed and it is in a "finished state".

   o STOP, just stop this transfer and consider it completed

   o PAUSE?

   o RESUME?

 DOCUMENTATION

 * More and better