bug#5482: frame-invisible-p reports nil for iconified frames on w32

[Lennart Borgman]

This problem happens for example under these circumstances:

Create a frame

  (setq my-frame (make-frame))

Iconify it. Then make it first invisible and then visible again:

  (make-frame-invisible my-frame)
  (make-frame-visible my-frame)

The result of checking if it is visible is now nil (should be `iconified'):

  (frame-visible-p my-frame)

This is with a fresh checkout from yesterday.


BTW the implementation of frame-visible-p seems a bit strange to me on
w32. It is easy to check visibility using GetWindowPlacement, but is
this used?