+ Display at least two digits for keycodes.
  * configure.ac:
    + ScreenUpdate is actually mandatory for our conio driver.

+ Use SLkp_getkey instead of SLang_getkey so that escape sequences are
      directly interpreted.
    + Major rehandling of the event code. All output drivers are now
      correctly separated.
  * src/graphics.c:
    + Fixed a compilation warning.
  * test/event.c:
    + More human-readable event printing.

+ Small event lister, similar to X11's xev.
  * src/graphics.c:
    + If possible, disable autorepeat in the X11 driver.
  * src/io.c:
    + Implemented CACA_EVENT_MOUSE_RELEASE in all drivers.
    + Button number support in CACA_EVENT_MOUSE_{PRESS,RELEASE}.