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/mac/carbon/dc.h

@@ -211,7 +211,7 @@ protected:
         wxCoord *x, wxCoord *y,
         wxCoord *descent = NULL,
         wxCoord *externalLeading = NULL,
-        wxFont *theFont = NULL) const;
+        const wxFont *theFont = NULL) const;
 
     virtual bool DoGetPartialTextExtents(const wxString& text, wxArrayInt& widths) const;