Inspector: spacer and VBox height, HBox width are in wrong units

Context: commit e65d6b8b (2013-05-10)

Steps:
1) Open or create a score with any of the above elements: vert. spacer, vert. box, horix. box
2) Look at the inspector data for each

Result: The height of the spacer and of the VBox and the width of the HBox are not in sp, as declared in the Inspector, but in other units; box sizes are probably in sp / spatium(), spacer height is probably in sp * spatium().

Note: Acting on the Inspector values -- either by typing or by pressing the spin buttons -- modifies the sizes by unexpected amounts.