More border rationalisation. GetDefaultBorder is now mostly defined in base class files.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@49893 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/aui/auibook.h

@@ -455,6 +455,8 @@ public:
     bool IsDragging() const { return m_is_dragging; }
 
 protected:
+    // choose the default border for this window
+    virtual wxBorder GetDefaultBorder() const { return wxBORDER_NONE; }
 
     void OnPaint(wxPaintEvent& evt);
     void OnEraseBackground(wxEraseEvent& evt);
@@ -580,6 +582,8 @@ public:
     // virtual bool AcceptsFocus() const { return false; }
 
 protected:
+    // choose the default border for this window
+    virtual wxBorder GetDefaultBorder() const { return wxBORDER_NONE; }
 
     // these can be overridden
     virtual void UpdateTabCtrlHeight();