[trunk] Scores from 1.2 with various voices have the rests repositioned

The rests of scores from 1.2 (or 1.0 or 1.1) are repositioned if there is more than one active voice.

That's cool if you are writing a score directly with 2.0, but this feature should be turned off if the score comes from a previous version, since in these, you did already place the rests in the correct places, and that subprogram messes everything up.

Thanks,
G.