/*
 * Get the "playlist" time of a song.
 *
 * Examples:
 *   # get the "playlist" time of the current song
 *   time = remote.playlist_time
 *
 *   # get the "playlist" time of song 23 in the playlist
 *   time = remote.playlist_time 23
 *
 */
static VALUE xr_pl_time(int argc, VALUE *argv, VALUE self) {