Fix doc-strings of 'display-buffer-*' functions (Bug#19461)

Fix doc-strings of 'display-buffer-*' functions (Bug#19461)

* lisp/window.el (display-buffer-in-atom-window)
(display-buffer-in-side-window, display-buffer-record-window)
(display-buffer-use-some-frame, display-buffer-same-window)
(display-buffer-reuse-window, display-buffer-pop-up-frame)
(display-buffer-pop-up-window, display-buffer-in-child-frame)
(display-buffer-in-direction, display-buffer-below-selected)
(display-buffer-at-bottom, display-buffer-in-previous-window)
(display-buffer-use-some-window)
(display-buffer--maybe-pop-up-frame-or-window)
(display-buffer--maybe-pop-up-frame): Fix doc-strings
(Bug#19461).