wxGTK fixes for the yesterday's addition of m_isWindow flag

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@1777 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/window.h

@@ -532,6 +532,9 @@ public:
     virtual void GetPositionConstraint(int *x, int *y) const ;
 
 protected:
+    // common part of all ctors
+    void Init();
+
     // this is the virtual function to be overriden in any derived class which
     // wants to change how SetSize() or Move() works - it is called by all
     // versions of these functions in the base class