* window.el (display-buffer-function, special-display-p)

* window.el (display-buffer-function, special-display-p)
(special-display-buffer-names, special-display-regexps)
(special-display-function, same-window-p, same-window-buffer-names)
(same-window-regexps, pop-up-frames, display-buffer-reuse-frames)
(pop-up-frame-function, pop-up-windows)
(split-window-preferred-function, split-height-threshold)
(split-width-threshold, window--splittable-p)
(window--try-to-split-window, window--frame-usable-p)
(even-window-heights, window--even-window-heights)
(window--display-buffer-1, window--display-buffer-2, display-buffer)
(pop-to-buffer): Move from window.c and buffer.c.
(split-window-preferred-horizontally): Remove.
* cus-start.el: Remove corresponding declarations.

* window.c (pop_up_windows, pop_up_frames)
(display_buffer_reuse_frames, Vpop_up_frame_function)
(Vdisplay_buffer_function, Veven_window_heights)
(Vspecial_display_buffer_names, Vspecial_display_regexps)
(Vspecial_display_function, Vsame_window_buffer_names)
(Vsame_window_regexps, split_height_threshold)
(Vsplit_window_preferred_function): Move those vars to window.el.
(display_buffer_1, Fspecial_display_p, Fsame_window_p)
(Fdisplay_buffer): Move those functions to window.el.
(syms_of_window): Remove corresponding declarations.
(display_buffer): New function.
(temp_output_buffer_show, Fother_window_for_scrolling): Use it.
* dispnew.c (Flast_nonminibuf_frame): New function.
* buffer.c (Fpop_to_buffer): Move to window.el.