routine was erasing and redrawing in one step, which ignored the
possibility of having to erase from one window and redraw in
another if the cursor moved focus from one window to another.
This led to crosshairs being improperly drawn and erased when
multiple windows were present, if the windows had different cells
loaded.
rescaling the internal units. The former in particular can
cause problems when moving the root box and importing cells from
a script (same change as made to magic-8.1).
Tim Edwards