+ Do not refresh after each event, but only when there is no event
      pending.
    + If the pressed key is a printable character, display it.
  * src/time.c:
    + Moved _caca_getticks() to this file.
  * src/caca.c:
    + Set the escape delay to a very low value in the ncurses driver,
      because I don't want escape sequences to be entered manually.
  * src/io.c:
    + Autorepeat emulation in the ncurses and slang drivers: do not
      immediately send the key release event.
  * configure.ac:
    + Check for usleep.
    + Improvements in the win32 platform detection.