/*
 * Get the ordinal (list position) of an item in a list.
 *
 * Normally used to retrieve the track number out of a list of tracks in
 * an album.
 *
 * Aliases:
 *   MusicBrainz::Client#get_ordinal
 *   MusicBrainz::Client#get_ordinal_from_list
 *
 * Examples:
 *   # get the ordinal of a track based on the URI
 *   list = mb.result MusicBrainz::Query::AlbumGetTrackList
 *   uri  = mb.result MusicBrainz::Query::AlbumGetTrackId, 5
 *   ordinal = mb.ordinal list, uri
 *   
 */
static VALUE mb_client_ordinal(VALUE self, VALUE list, VALUE uri) {