Slurs too flat in some cases

Slurs with that include a note much higher than the start/end points are not drawn sufficiently curved. The result is that when autoplace moves them up to avoid the collision with the high note, the end points are too far away from the notes:

There's kind of a lot to consider if we want to create truly "optimum" slurs 9and decide when that means, it's OK for them to be asymmetric), but I'll be submitting a PR to do a fairly simple adjustment to improve some basic cases.