Rewrite window/frame auto-deletion code. (Bug#9419) and (Bug#9456)
* window.el (frame-auto-delete): Rename to window-auto-delete.
Make it control auto-deletion of windows and/or frames.
(window-deletable-p): New argument FORCE. Rewrite conditions
for deleting window/frame. (Bug#9419)
(switch-to-prev-buffer, replace-buffer-in-windows, quit-window):
Rewrite handling of case when window/frame can be deleted.
(delete-windows-on): Call window-deletable-p with new FORCE
argument t. (Bug#9456)