/*
 * Return the number of axes for this joystick.
 *
 * Note: Don't forget that each joypad has two axes.
 * 
 * Aliases:
 *   Joystick::Device#num_axes
 *
 * Example:
 *   puts "This joystick has #{joy.axes / 2} pads."
 * 
 */
static VALUE j_dev_axes(VALUE self) {