Simplify normalization of default buffer display specifieres and options.

Simplify normalization of default buffer display specifieres and options.

* window.el (display-buffer-default-specifiers): Remove.
(display-buffer-macro-specifiers): Remove default specifiers.
(display-buffer-alist): Default to nil.
(display-buffer-reuse-window): New optional argument
other-window.
(display-buffer-pop-up-window): Allow splitting internal
windows.  Check whether a live window was created.
(display-buffer-other-window-means-other-frame)
(display-buffer-normalize-arguments): Rename to
display-buffer-normalize-argument and rewrite.  Set the
other-window specifier.
(display-buffer-normalize-special): New function.
(display-buffer-normalize-options): Rename to
display-buffer-normalize-default and rewrite.
(display-buffer-normalize-options-inhibit): Remove.
(display-buffer-normalize-specifiers): Rewrite.
(display-buffer): Process other-window specifier and call
display-buffer-reuse-window with it.  Emulate Emacs 23 behavior
more faithfully.
(pop-up-windows, even-window-heights): Restore Emacs 23 default
values.
(display-buffer-alist-set): Don't handle 'unset default values.
(display-buffer-in-window, display-buffer-alist-set): Replace
symbol "dedicated" by "dedicate".  Reported by Tassilo Horn
<tassilo@member.fsf.org>.