Hilite the terrain the mouse is over in the scenario editor so that you can tell which terrain will be affected when clicking, even in cases where it's not so obvious (for example when the cursor's hotspot is in an unexpected place).

src/scenedit/scen.actions.h

@@ -52,6 +52,7 @@ void start_special_editing(short mode,short just_redo_text);
 void town_entry(location spot_hit);
 void start_dialogue_editing(short restoring);
 bool is_erasable_water(short i,short j);
+void update_mouse_spot(location the_point);
 
 bool monst_on_space(location loc,short m_num);
 void place_edit_special(location loc);