Changed some documentation.

Changed some documentation.
(view-exits-all-viewing-windows): Nev variable
replaces view-exit-all-windows-at-exit.
(view-exit-all-windows-at-exit): Variable deleted.
(view-mode-enter): Doesn't set view-exit-action	if
argument exit-action is nil.
(view-mode-exit): Only restored windows are removed
from view-return-to-alist.  Follow chains of old-windows.
Do not call replace-buffer-in-windows.
Call exit-action also when a window displays buffer.
(View-exit-and-edit): Now sets read-only by binding
view-old-buffer-read-only.