Pitch bend tuning fixes

Pitch bend tuning fixes

1) The pitch isn't always rounded to the nearest equally
tempered value, so the result looks strange in a sequencer,
and artifacts caused by the pitch bends are more severe.

2) The tuning is rounded to cents before the pitch bends
are calculated.  It may not be a big deal, but there's no
need for it, and the code's simpler calculating the bends
directly.