ScenEditor: create a class to store some static buttons and scrollbars

+ begin to use it, to be continued...

src/scenedit/scen.graphics.hpp

@@ -10,10 +10,6 @@ void run_startup_g();
 void load_graphics();
 void draw_main_screen();
 void redraw_screen();
-void draw_lb();
-void draw_lb_slot (short which,short mode) ;
-void draw_rb();
-void draw_rb_slot (short which,short mode) ;
 void set_up_terrain_buttons(bool reset);
 void draw_terrain();
 void draw_monsts();