Don't handle splits status.

Don't handle splits status.

* window.h (window): Remove splits slot.
* window.c (Fwindow_splits, Fset_window_splits): Remove.
(Fdelete_other_windows_internal, make_parent_window)
(make_window, Fsplit_window_internal, Fdelete_window_internal)
(Fset_window_configuration, save_window_save): Don't deal with
split status of windows.
(saved_window): Remove splits slot.
(Vwindow_splits): Rewrite doc-string.
* window.el (window-resize, delete-window): Use window-splits
variable instead of function.
(window-state-get-1, window-state-put-2, window-state-put):
Don't deal with windows' splits status.
* windows.texi (Splitting Windows, Deleting Windows): Remove
references to splits status of windows.