Doc changes related to displaying buffers and quitting windows.

Doc changes related to displaying buffers and quitting windows.

* window.el (switch-to-visible-buffer)
(switch-to-buffer-preserve-window-point): Fix doc-strings.

* windows.texi (Switching Buffers): Document option
switch-to-buffer-preserve-window-point.
(Display Action Functions): Document window-height and
window-width alist entries.
(Display Action Functions): Document
display-buffer-below-selected and
display-buffer-in-previous-window.
(Quitting Windows): Document quit-restore-window.  Rewrite
section.
(Window Configurations): In window-state-get mention that
argument window must be valid.
(Window Parameters): Document quit-restore window parameter
(Bug#12158).