/*
 * Convert 16-byte raw signature into a human-readable 36-byte ASCII string.
 *
 * Used after MusicBrainz::TRM#generate_signature has returned true and
 * MusicBrainz::TRM#finalize_signature has returned a signature.
 *
 * Aliases:
 *   MusicBrainz::TRM#sig_to_ascii
 *   MusicBrainz::TRM#convert_sig_to_ascii
 *
 * Examples:
 *   puts 'signature: ' << trm.convert_sig raw_sig
 *
 */
static VALUE mb_trm_convert_sig(VALUE self, VALUE sig) {