Make ComputeScaleAndOrigin() as virtual part of wxDCBase and this way present on missing platforms. Add into manaul too.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@31034 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/dc.h

@@ -530,6 +530,8 @@ public:
         { wxCoord x, y; DoGetDeviceOrigin(&x, &y); return wxPoint(x, y); }
     virtual void SetDeviceOrigin(wxCoord x, wxCoord y) = 0;
 
+    virtual void ComputeScaleAndOrigin() {}
+
     virtual void SetAxisOrientation(bool xLeftRight, bool yBottomUp) = 0;
 
     int GetLogicalFunction() const { return m_logicalFunction; }