Fix some more display-buffer related bugs.

Fix some more display-buffer related bugs.

* window.el (display-buffer-normalize-argument): Rename to
display-buffer-normalize-arguments.  Handle special meaning of
LABEL argument.  Respect special-display-function when popping
up a new frame.  Fix code searching for a window showing the
buffer on another frame.
(display-buffer-normalize-specifiers): Call
display-buffer-normalize-arguments.
(display-buffer-in-window): Don't undedicate the window if its
buffer remains the same.
Reported by Drew Adams <drew.adams@oracle.com>.
(display-buffer-alist): Add choice for same-window macro
specfier.
(display-buffer): Mention special meaning of LABEL argument in
doc-string.  Fix quoting.  Don't pop up a new frame even as
fallback.