returns a full-width window if possible.
@defun get-lru-window &optional frame
This function returns the window least recently ``used'' (that is,
-selected). The selected window is always the most recently used window.
+selected). If any full-width windows are present, it only considers
+these. The selected window is always the most recently used window.
The selected window can be the least recently used window if it is the
only window. A newly created window becomes the least recently used