fixed deleting pages from the notebook

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@10794 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/notebook.h

@@ -155,7 +155,7 @@ public:
 
 protected:
     // remove the page and return a pointer to it
-    virtual wxNotebookPage *DoRemovePage(int page) = 0;
+    virtual wxNotebookPage *DoRemovePage(int page);
 
     // common part of all ctors
     void Init();