Some fixes and improvements for desktop frame restoration.

Some fixes and improvements for desktop frame restoration.
It is still experimental and disabled by default.

* lisp/desktop.el (desktop--save-windows): Put the selected frame at
  the head of the list.
  (desktop--make-full-frame): New function.
  (desktop--restore-windows): Try to re-select the frame that was
  selected upon saving.  Do not abort if some frames fail to restore,
  just show an error message and contnue.  Set up maximized frames so
  they have default non-maximized dimensions.