bug#67993: Selecting buffer automatically

[martin rudalics]

> Martin, do you agree with this change?
> If ok, then I could update the documentation as well.

The following looks like a glitch:

>> +                      (when (window-live-p (old-selected-window))
>> +                        (select-window (old-selected-window))))

is supposed to select the window selected the last time we ran window
change functions.  Now consider the following scenario:

- Redisplay runs the window change functions and sets the old selected
  window.

- An application changes the selected window.

- 'display-buffer' gets called with a (select-window . nil) entry.  The
  call will select the window selected at last redisplay.

So I think that calling 'old-selected-window' here is not TRT.

martin