OSX specific, related to the wxWidgets 3.1.4: Fixed wrong UI-scaling

(wxWidgets 3.1.4 can binding of wxEVT_DPI_CHANGED now, so it was called msw_rescale() for most of the controls redundantly)

+ Fixed update of the DoubleSlider after changing of the system color

src/slic3r/GUI/GUI_Utils.hpp

@@ -108,6 +108,7 @@ public:
 
 //        recalc_font();
 
+#ifndef __WXOSX__
 #if wxVERSION_EQUAL_OR_GREATER_THAN(3,1,3)
         this->Bind(wxEVT_DPI_CHANGED, [this](wxDPIChangedEvent& evt) {
 	            m_scale_factor = (float)evt.GetNewDPI().x / (float)DPI_DEFAULT;
@@ -128,6 +129,7 @@ public:
                 rescale(evt.rect);
             });
 #endif // wxVERSION_EQUAL_OR_GREATER_THAN
+#endif // no __WXOSX__
 
         this->Bind(wxEVT_MOVE_START, [this](wxMoveEvent& event)
         {