Rewrite switch-to-prev-/next-buffer and quit-window; add display-buffer-below-selected.

Rewrite switch-to-prev-/next-buffer and quit-window; add display-buffer-below-selected.

* window.el (switch-to-prev-buffer): Handle additional values of
BURY-OR-KILL argument.  Don't switch in minibuffer window.
(switch-to-next-buffer): Don't switch in minibuffer window.
(quit-restore-window): New function based on quit-window.
Handle additional values of former KILL argument.
(quit-window): Call quit-restore-window with appropriate
interpretation of KILL argument.
(display-buffer-below-selected): New buffer display action
function.