cannot set window-size-fixed to 'height or 'width

[martin rudalics]

According to the Elisp manual:

 -- Variable: window-size-fixed
     ...
     If the value is `height', then only the window's height is fixed;
     if the value is `width', then only the window's width is fixed.
     Any other non-`nil' value fixes both the width and the height.

But `window.c' has:

  DEFVAR_BOOL ("window-size-fixed", &window_size_fixed,
               doc: /* Non-nil in a buffer means ...

Hence (setq window-size-fixed 'height) and (setq window-size-fixed
'width) always set `window-size-fixed' t.