Add an #ifdef to shut gtk-doc up

gtk-doc complains that the stock macros are deprecated,
but not in an #ifdef block. So add one.

gtk/deprecated/gtkstock.h

@@ -106,6 +106,8 @@ G_DEPRECATED
 #endif
 typedef char * GtkStock;
 
+#ifndef GTK_DISABLE_DEPRECATED
+
 /* Stock IDs (not all are stock items; some are images only) */
 /**
  * GTK_STOCK_ABOUT:
@@ -1261,6 +1263,8 @@ typedef char * GtkStock;
  */
 #define GTK_STOCK_ZOOM_OUT         ((GtkStock)"gtk-zoom-out")
 
+#endif
+
 G_END_DECLS
 
 #endif /* __GTK_STOCK_H__ */