Fix 'display-buffer-use-least-recent-window'

Fix 'display-buffer-use-least-recent-window'

* src/window.c (Fwindow_use_time): Doc fix.
(Fwindow_bump_use_time): Bump use time of the seleceted window as
well.  Doc fix.

* lisp/window.el (display-buffer-avoid-small-windows): Remove.
All users changed.
(window--display-buffer): Bump window use time when requested.
(display-buffer--lru-window): New function.
(display-buffer-use-some-window): Use it.
(display-buffer-use-least-recent-window): Rewrite and enhance doc
string.

* doc/lispref/windows.texi (Selecting Windows)
(Buffer Display Action Functions, Buffer Display Action Alists)
(The Zen of Buffer Display): Improve and update documentation of
window selection and display facilities.