/* 
 * Return the value of this Joystick::Event object.
 *
 * The content of Joystick::Event#value varies depending on the type of
 * event.  For Joystick::Event::AXIS events, the value is the direction
 * (and optionally magnitude) of the axis (eg, -32767 for maximum
 * right/up, 19931 for partial left/down, etc).  For
 * Joystick::Event:BUTTON events, the value is usually 1 or 0, for
 * button presses and button releases, respectively.
 * 
 * Aliases:
 *   Joystick::Event#val
 *
 * Example:
 *   puts "The button was " << 
 *        ((ev.value != 0) ? 'pressed' : 'released') <<
 *        "." if ev.type == Joystick::Event::BUTTON
 *
 */
static VALUE j_ev_value(VALUE self) {