Implement wxNotebook::CalcSizeFromPage() for wxGTK.

The implementation is far from perfect as it relies on hard-coded margins but
is better than nothing as it allows wxNotebook best size determination and
SetPageSize() method to work correctly.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70112 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/notebook.h

@@ -68,13 +68,13 @@ public:
   bool SetPageImage(size_t nPage, int nImage);
 
   // control the appearance of the notebook pages
-    // set the size (the same for all pages)
-  void SetPageSize(const wxSize& size);
     // set the padding between tabs (in pixels)
   void SetPadding(const wxSize& padding);
     // sets the size of the tabs (assumes all tabs are the same size)
   void SetTabSize(const wxSize& sz);
 
+  // geometry
+  virtual wxSize CalcSizeFromPage(const wxSize& sizePage) const;
   virtual int HitTest(const wxPoint& pt, long *flags = NULL) const;
 
   // operations