FIX: use wxMessageDialog as warning in MAC

jira: [STUDIO-10386]
Change-Id: Ic8cc6d09f2eba41ec8cfebf239eb6bd78dd3844a
(cherry picked from commit 1537f575927f8d0f0e2658f900296344deb6682c)
(cherry picked from commit a856c7cc62636a4897b0e473034579e223808a7b)

src/slic3r/GUI/Widgets/TempInput.hpp

@@ -118,6 +118,7 @@ public:
 
     wxTextCtrl const *GetTextCtrl() const { return text_ctrl; }
 
+    bool  IsOnChanging() const { return m_on_changing; }
     void  SetOnChanging() { m_on_changing = true; }
     void  ReSetOnChanging() { m_on_changing = false; }