bug#22247: 24.4; ghost mouse pointer

[Pierpaolo Bernardi <olopierpa@gmail.com>]

In GNU Emacs 24.4.1 (i686-pc-mingw32)
 of 2014-10-24 on LEG570
Windowing system distributor `Microsoft Corp.', version 6.2.9200
Configured using:
 `configure --prefix=/c/usr'

(But also in older versions both of Emacs and of Windows. This is
present since the first time I used Emacs on windows, around 15 years
ago).

I use this function to move the mouse pointer out of my way:

    (defun move-cursor-out ()
      (interactive)
      (set-mouse-position (window-frame (frame-selected-window))
                          (1+ (frame-width))
                          0))

    (global-set-key [f12] 'move-cursor-out)

This works as intended on Unix/X.

On windows, the mouse pointer is moved in the right place, but a ghost
image of the pointer is left behind in the old position *most of the
times* (not always), thus vanifying the purpose of the code.

Thanks!