bug#45052: 27.1; GDB completion moves point

[Eli Zaretskii]

> From: "Philip K." <philipk@posteo.net>
> Date: Sat, 05 Dec 2020 13:10:46 +0100
> 
> 1. M-x gdb
> 2. Press enter a few times, so that the buffer can't fit into the window
> 3. Ensure that the point is in the last few lines (C-l)
> 4. Enter "l" and then press M-tab.
> 
> The point should now have been moved. This is not expected, and not seen
> any other mode.

Does the patch below give good results, and doesn't produce any
adverse effects in other use cases?

diff --git a/lisp/progmodes/gdb-mi.el b/lisp/progmodes/gdb-mi.el
index 9030056..2b9a9c1 100644
--- a/lisp/progmodes/gdb-mi.el
+++ b/lisp/progmodes/gdb-mi.el
@@ -3010,7 +3010,7 @@ def-gdb-auto-update-handler
        (,custom-defun)
        (gdb-update-buffer-name)
        ,@(when (not nopreserve)
-          '((set-window-start window start)
+          '((set-window-start window start t)
             (set-window-point window p))))))
 
 (defmacro def-gdb-trigger-and-handler (trigger-name gdb-command