* lisp/image-mode.el: Use lexical-binding.

* lisp/image-mode.el: Use lexical-binding.
(image-mode-winprops): Use t to stand for the window of a buffer that's
not displayed.
* lisp/doc-view.el (doc-view-new-window-function): Handle t in winprops.
(doc-view-enlarge): Make it a real nop if the size is not changed.
(doc-view-display): Handle the case where the buffer is not (yet?)
displayed in any window.
(doc-view-saved-settings): New var.
(doc-view-mode): Use it.
(doc-view-fallback-mode): Set it.