/*
 * call-seq:
 *      update( summ, msg, icon )
 *
 * summ = The new summary text ( required )
 *
 * msg = The new body text or nil
 *
 * icon = The new icon or nil
 *
 * This won't send the update out and display it on the screen.
 * For that, you will need to call the show method.
 *
 * return TRUE if ok or FALSE otherwise
 */
static VALUE
notification_update( VALUE self, VALUE summ, VALUE msg, VALUE icon ) {