make wxMask pixmap member private

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70951 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/bitmap.h

@@ -30,7 +30,7 @@ public:
     virtual ~wxMask();
 
     // implementation
-    GdkPixmap* m_bitmap;
+    wxMask(GdkPixmap*);
     GdkPixmap* GetBitmap() const;
 
 protected:
@@ -38,6 +38,9 @@ protected:
     virtual bool InitFromColour(const wxBitmap& bitmap, const wxColour& colour);
     virtual bool InitFromMonoBitmap(const wxBitmap& bitmap);
 
+private:
+    GdkPixmap* m_bitmap;
+
     DECLARE_DYNAMIC_CLASS(wxMask)
 };