Pass wxRect/wxPoint arguments to wxDataViewCustomRenderer by reference.

Instead of passing them by value, use const reference. This change
is safe to do, because these methods' signatures were different in 2.8
anyhow.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67099 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/dvrenderer.h

@@ -47,14 +47,14 @@ public:
     // generic implementation uses these ones for all of them, including the
     // standard ones.
 
-    virtual bool WXOnActivate(wxRect WXUNUSED(cell),
+    virtual bool WXOnActivate(const wxRect& WXUNUSED(cell),
                               wxDataViewModel *WXUNUSED(model),
                               const wxDataViewItem & WXUNUSED(item),
                               unsigned int WXUNUSED(col))
         { return false; }
 
-    virtual bool WXOnLeftClick(wxPoint WXUNUSED(cursor),
-                               wxRect WXUNUSED(cell),
+    virtual bool WXOnLeftClick(const wxPoint& WXUNUSED(cursor),
+                               const wxRect& WXUNUSED(cell),
                                wxDataViewModel *WXUNUSED(model),
                                const wxDataViewItem & WXUNUSED(item),
                                unsigned int WXUNUSED(col) )