declare GetGDKWindow() in wxDC to fix compilation of wxRendererNative

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45854 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk1/dc.h

@@ -38,6 +38,8 @@ public:
     virtual void StartPage() { }
     virtual void EndPage() { }
 
+    virtual GdkWindow* GetGDKWindow() const { return NULL; }
+
 public:
     // implementation
     wxCoord XDEV2LOG(wxCoord x) const       { return DeviceToLogicalX(x); }