/*
 * Get the balance level.
 *
 * Note: as of XMMS 1.2.6 xmms_remote_get_balance() does not appear to
 * work correctly when XMMS is paused or stopped, so this function doesn't
 * either.
 * 
 * Example:
 *   vol = remote.balance
 *
 */
static VALUE xr_balance(VALUE self) {