Respect selection color in monitor widget

We should have a consistent color set over all widgets.

vncviewer/fltk/Fl_Monitor_Arrangement.cxx

 Fl_Monitor_Arrangement::Fl_Monitor_Arrangement(
    int x, int y, int w, int h)
 :  Fl_Group(x, y, w, h),
-   SELECTION_COLOR(fl_lighter(FL_BLUE)),
    AVAILABLE_COLOR(fl_lighter(fl_lighter(fl_lighter(FL_BACKGROUND_COLOR))))
 {
   // Used for required monitors.
 
     if (is_required(iter->first)) {
       monitor->box(FL_CHECKERED_BOX);
-      monitor->color(SELECTION_COLOR);
+      monitor->color(FL_SELECTION_COLOR);
     } else {
       monitor->box(FL_BORDER_BOX);
       monitor->color(AVAILABLE_COLOR);
-      monitor->selection_color(SELECTION_COLOR);
+      monitor->selection_color(FL_SELECTION_COLOR);
     }
   }
 

vncviewer/fltk/Fl_Monitor_Arrangement.h

   virtual void draw();
 
 private:
-  const Fl_Color SELECTION_COLOR;
   const Fl_Color AVAILABLE_COLOR;
   typedef std::map<int, Fl_Button *> MonitorMap;
   MonitorMap monitors;