patch 9.1.0147: Cannot keep a buffer focused in a window

Problem:  Cannot keep a buffer focused in a window
          (Amit Levy)
Solution: Add the 'winfixbuf' window-local option
          (Colin Kennedy)

fixes:  #6445
closes: #13903

Signed-off-by: Colin Kennedy <colinvfx@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/message.txt b/runtime/doc/message.txt
index 133d47a..5848074 100644
--- a/runtime/doc/message.txt
+++ b/runtime/doc/message.txt
@@ -1,4 +1,4 @@
-*message.txt*   For Vim version 9.1.  Last change: 2023 Dec 20
+*message.txt*   For Vim version 9.1.  Last change: 2024 Mar 03
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -122,6 +122,13 @@
 You cannot have two buffers with exactly the same name.  This includes the
 path leading to the file.
 
+							*E1513* >
+  Cannot edit buffer. 'winfixbuf' is enabled
+
+If a window has 'winfixbuf' enabled, you cannot change that window's current
+buffer. You need to set 'nowinfixbuf' before continuing. You may use [!] to
+force the window to switch buffers, if your command supports it.
+
 							*E72*
   Close error on swap file ~