patch 8.1.1218: cannot set a directory for a tab page

Problem:    Cannot set a directory for a tab page.
Solution:   Add the tab-local directory. (Yegappan Lakshmanan, closes #4212)
diff --git a/runtime/doc/autocmd.txt b/runtime/doc/autocmd.txt
index edd1f54..5d60fbe 100644
--- a/runtime/doc/autocmd.txt
+++ b/runtime/doc/autocmd.txt
@@ -1,4 +1,4 @@
-*autocmd.txt*   For Vim version 8.1.  Last change: 2019 Apr 08
+*autocmd.txt*   For Vim version 8.1.  Last change: 2019 Apr 27
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -690,13 +690,14 @@
 				change or when doing |:diffupdate|.
 							*DirChanged*
 DirChanged			The working directory has changed in response
-				to the |:cd| or |:lcd| commands, or as a
-				result of the 'autochdir' option.
+				to the |:cd| or |:tcd| or |:lcd| commands, or
+				as a result of the 'autochdir' option.
 				The pattern can be:
-					"window" to trigger on `:lcd`
-					"global" to trigger on `:cd`
-					"auto"   to trigger on 'autochdir'.
-					"drop"	 to trigger on editing a file
+					"window"  to trigger on `:lcd`
+					"tabpage" to trigger on `:tcd`
+					"global"  to trigger on `:cd`
+					"auto"    to trigger on 'autochdir'.
+					"drop"	  to trigger on editing a file
 				<afile> is set to the new directory name.
 							*ExitPre*
 ExitPre				When using `:quit`, `:wq` in a way it makes