patch 9.0.1546: some commands for opening a file don't use 'switchbuf'

Problem:    Some commands for opening a file don't use 'switchbuf'.
Solution:   Use 'switchbuf' for more commands. (Yegappan Lakshmanan,
            closes #12383, closes #12381)
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 2a2c7ed..c487f17 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -7928,16 +7928,18 @@
 'switchbuf' 'swb'	string	(default "")
 			global
 	This option controls the behavior when switching between buffers.
-	Mostly for |quickfix| commands some values are also used for other
-	commands, as mentioned below.
+	This option is checked, when
+	- jumping to errors with the |quickfix| commands (|:cc|, |:cn|, |:cp|,
+	  etc.)
+	- jumping to a tag using the |:stag| command.
+	- opening a file using the |CTRL-W_f| or |CTRL-W_F| command.
+	- jumping to a buffer using a buffer split command (e.g.  |:sbuffer|,
+	  |:sbnext|, or |:sbrewind|).
 	Possible values (comma-separated list):
-	   useopen	If included, jump to the first open window that
-			contains the specified buffer (if there is one).
-			Otherwise: Do not examine other windows.
-			This setting is checked with |quickfix| commands, when
-			jumping to errors (":cc", ":cn", "cp", etc.).  It is
-			also used in all buffer related split commands, for
-			example ":sbuffer", ":sbnext", or ":sbrewind".
+	   useopen	If included, jump to the first open window in the
+			current tab page that contains the specified buffer
+			(if there is one).  Otherwise: Do not examine other
+			windows.
 	   usetab	Like "useopen", but also consider windows in other tab
 			pages.
 	   split	If included, split the current window before loading