message: Using u32 constants for LED instructions
diff: use syscalls::command;
  +const COUNT: u32 = 0;
  +const ON: u32 = 1;
  +const OFF: u32 = 2;
  +const TOGGLE: u32 = 3;
  +
  pub fn count() -> isize {
  - command(8, 0, 0)
  + command(8, COUNT, 0)
  }
  pub fn on(led_num: u32) {
  - command(8, 1, led_num as isize);
  + command(8, ON, led_num as isize);
  }
  pub fn off(led_num: u32) {
  - command(8, 2, led_num as isize);
  + command(8, OFF, led_num as isize);
  }
  pub fn toggle(led_num: u32) {
  - command(8, 3, led_num as isize);
  + command(8, TOGGLE, led_num as isize);
  }
  -
  