lisp/desktop.el: More fixes to frame restoration.

lisp/desktop.el: More fixes to frame restoration.
(desktop-restore-frames): Rename from desktop-save-windows.
(desktop-restore-in-current-display): New customization option.
(desktop--excluded-frame-parameters): Add `font'.
(desktop--save-frames): Rename from desktop--save-windows.
(desktop--restore-in-this-display-p): New function.
(desktop--make-full-frame): Remove unwanted width/height from
full(width|height) frames.
(desktop--restore-frames): Rename from desktop--restore-windows.
Obey desktop-restore-current-display.  Do not delete old frames or
select a new frame unless we were able to restore at least one frame.