bug#30792: 26.0.91; improve docstring of with-help-window

[martin rudalics <rudalics@gmx.at>]

 >> It strikes me that instead of repeating most of what
 >> with-temp-buffer-window's doc string says, it might be better to
 >> simply refer to there.  Like this:
 >>
 >>    Display the output produced by evaluating BODY, like
 >>    `with-temp-buffer-window' does, then put the window in
 >>    `help-mode' [...]

Neither `with-temp-buffer-window' nor `help-mode' are of any relevance
here.  The distinctive aspect of `with-help-window' is provided by
`help-window-setup' which sets up the help window for quitting it
later.  Earlier macros failed miserably in this regard.  (I have to
admit that many people are still ignorant of this fact and believe
they could resolve the quitting problem by saving and restoring window
configurations.  So the old doc-string probably failed to provide this
rather crucial information as well.)

 > +This construct is like `with-current-buffer-window' but unlike that

IIUC it does not make the buffer current when running BODY.

martin