changed wxDC::GetTextExtent() and related methods to take const wxFont pointer, for consistency with wxWindow::GetTextExtent() and because it generally doesn't need a non-const font

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45638 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/metafile.h

@@ -90,7 +90,7 @@ public:
     virtual void SetMapMode(int mode);
     virtual void GetTextExtent(const wxString& string, long *x, long *y,
             long *descent = NULL, long *externalLeading = NULL,
-            wxFont *theFont = NULL, bool use16bit = false) const;
+            const wxFont *theFont = NULL, bool use16bit = false) const;
 
     // Implementation
     wxMetafile *GetMetaFile() const { return m_metaFile; }