GTK+ cell renderers are not widget, so use a

correct type.
  Also found a way to set cell background and
   probably other styles.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45914 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/defs.h

@@ -2848,6 +2848,7 @@ typedef struct _GtkItemFactory    GtkItemFactory;
 typedef struct _GtkSelectionData  GtkSelectionData;
 typedef struct _GtkTextBuffer     GtkTextBuffer;
 typedef struct _GtkRange          GtkRange;
+typedef struct _GtkCellRenderer   GtkCellRenderer;
 
 typedef GtkWidget *WXWidget;