Moves the iterator forward one metadata block, returning \c false if
already at the end.
\param iterator A pointer to an existing initialized iterator.
\assert
\code iterator != NULL \endcode
\a iterator has been successfully initialized with
FLAC__metadata_iterator_init()
\retval FLAC__bool
\c false if already at the last metadata block of the chain, else
\c true.
Moves the iterator forward one metadata block, returning \c false if already at the end.
\param iterator A pointer to an existing initialized iterator. \assert \code iterator != NULL \endcode \a iterator has been successfully initialized with FLAC__metadata_iterator_init() \retval FLAC__bool \c false if already at the last metadata block of the chain, else \c true.