Improve splitting lists of copyright holders

[pombredanne]

With:

        (c) 1999                Terrehon Bowden <terrehon@pacbell.net>
                                Bodo Bauer <bb@ricochet.net>

we get

       copyrights:
           -   copyright: (c) 1999 Terrehon Bowden <terrehon@pacbell.net> Bodo Bauer <bb@ricochet.net>
       holders:
           -   holder: Terrehon Bowden Bodo Bauer

ideally we should get this instead

       holders:
           -   holder: Terrehon Bowden
           -   holder: Bodo Bauer

The parse tree looks like this, so we have distinct name groups to guide splitting:

(label='ROOT', children=(
    (label='COPYRIGHT', children=(
        (label='COPY', value='(c)')
        (label='NAME-YEAR', children=(
            (label='NAME-YEAR', children=(
                (label='NAME-YEAR', children=(
                    (label='YR-RANGE', children=(
                        (label='YR-RANGE', children=(
                            (label='YR', value='1999')
                        ))
                    ))
                    (label='NNP', value='Terrehon')
                    (label='NNP', value='Bowden')
                ))
            ))
        ))
        (label='NAME-EMAIL', children=(
            (label='NAME', children=(
                (label='EMAIL', value='<terrehon@pacbell.net>')
                (label='NAME', children=(
                    (label='NNP', value='Bodo')
                    (label='NNP', value='Bauer')
                ))
            ))
            (label='EMAIL', value='<bb@ricochet.net>')
        ))
    ))
))