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/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 5bb763a..c579ed2 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -10357,8 +10357,13 @@
 tabpagenr([{arg}])					*tabpagenr()*
 		The result is a Number, which is the number of the current
 		tab page.  The first tab page has number 1.
-		When the optional argument is "$", the number of the last tab
-		page is returned (the tab page count).
+
+		The optional argument {arg} supports the following values:
+			$	the number of the last tab page (the tab page
+				count).
+			#	the number of the last accessed tab page
+				(where |g<Tab>| goes to). if there is no
+				previous tab page 0 is returned.
 		The number can be used with the |:tab| command.