Axis_group_interface::relative_pure_height (Grob *me, int start, int end)
{
/* It saves a _lot_ of time if we assume a VerticalAxisGroup is additive
Axis_group_interface::relative_pure_height (Grob *me, int start, int end)
{
/* It saves a _lot_ of time if we assume a VerticalAxisGroup is additive