THINGS TO DO

(These should be resolved before releasing the next version.)

Ensure that redraw being done on see-always units changing sides
in tcltk interface.

Fix wind speed/acp calcs for voyages.

Fix usage of update_cell_display bitmask in mac interface.

Fix dragging behavior of scrollbar thumbs.

Fix behavior of protection table.

Fix when acp < 0 and acp-min < 0 so that multiple move-to actions
during turn will work.
