patch 8.2.1401: cannot jump to the last used tabpage

Problem:    Cannot jump to the last used tabpage.
Solution:   Add g<Tab> and tabpagnr('#'). (Yegappan Lakshmanan, closes #6661,
            neovim #11626)
diff --git a/src/globals.h b/src/globals.h
index cc01ac2..72b8a1e 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -725,10 +725,12 @@
 
 /*
  * Tab pages are alternative topframes.  "first_tabpage" points to the first
- * one in the list, "curtab" is the current one.
+ * one in the list, "curtab" is the current one. "lastused_tabpage" is the
+ * last used one.
  */
 EXTERN tabpage_T    *first_tabpage;
 EXTERN tabpage_T    *curtab;
+EXTERN tabpage_T    *lastused_tabpage;
 EXTERN int	    redraw_tabline INIT(= FALSE);  // need to redraw tabline
 
 /*