patch 8.2.0909: cannot go back to the previous local directory

Problem:    Cannot go back to the previous local directory.
Solution:   Add "tcd -" and "lcd -". (Yegappan Lakshmanan, closes #4362)
diff --git a/runtime/doc/editing.txt b/runtime/doc/editing.txt
index f33ffb9..fae7118 100644
--- a/runtime/doc/editing.txt
+++ b/runtime/doc/editing.txt
@@ -1326,6 +1326,10 @@
 							*:tch* *:tchdir*
 :tch[dir][!]		Same as |:tcd|.
 
+							*:tcd-*
+:tcd[!] -		Change to the previous current directory, before the
+			last ":tcd {path}" command.
+
 							*:lc* *:lcd*
 :lc[d][!] {path}	Like |:cd|, but only set the current directory when
 			the cursor is in the current window.  The current
@@ -1335,6 +1339,10 @@
 							*:lch* *:lchdir*
 :lch[dir][!]		Same as |:lcd|.
 
+							*:lcd-*
+:lcd[!] -		Change to the previous current directory, before the
+			last ":lcd {path}" command.
+
 							*:pw* *:pwd* *E187*
 :pw[d]			Print the current directory name.
 			Also see |getcwd()|.