Anchor should snap to nearest anchor point when adjusting spanners with mouse

1. Drag a line (such as Prima Volta) to a measure in the score
2. Double-click volta bracket
3. Drag right anchor over two additional measures (notice dotted line indicating current anchor point)

Expect behavior: Anchor position should snap to closest measure for the new position.

Actual behavior: Anchor positions lock after dropping a line onto the score. Adjusting the handles afterward with the mouse leaves the anchor positions in place.

Discussion: Misunderstanding about anchors has come up several times of the forums (for one example see http://www.musescore.org/en/node/1563 ). I can't think of an instance where you would actually want the anchor position in a place other than the actual handle.