Rename of divide_AC_by_8 leftover from changeset 3381d2a.
Document in_permitted_area. Also split it into two routines.
Document plot_menu_text, now plot_statics_and_menu_text.

* counter_of_something is now plot_static_tiles_direction: a flag which indicates in which orientation to plot.
* counter_set_* are now plot_static_tiles_*
* The '0' and '255' entry points are now 'horizontal' and 'vertical' respectively.