in wxAuiNotebook, prevent unwanted page selection changes during tab drags

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@47055 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/aui/auibook.h

@@ -446,6 +446,10 @@ public:
 
     ~wxAuiTabCtrl();
 
+#if wxABI_VERSION >= 20805
+    bool IsDragging() const { return m_is_dragging; }
+#endif
+
 protected:
 
     void OnPaint(wxPaintEvent& evt);