bug#16681: mouse-autoselect-window missing when switching frames

[martin rudalics <rudalics@gmx.at>]

 > In a system with "focus follows mouse" do the following:
 >
 >    % src/emacs -Q --eval '(setq mouse-autoselect-window t)'
 >    C-x 5 2
 >    <place the two frames side by side>
 >    C-x 2
 >    <go to the second frame>
 >    C-x 2
 >
 > Now move mouse "in circle":
 > - top-left window, then top-right window, then bottom-right window, then
 >   bottom-left window, and if you like it, you can keep doing it for a while.
 > notice how this *should* select each one of the four windows in each cycle,
 > but instead only 2 of those windows are selected: when crossing from one
 > frame to the other the new frame is selected, but that frame's selected
 > window is used as the new selected window instead of using that the
 > window into which the mouse just entered.

Works without problems on Window XP.  On my Debian GTK build I have to
set `focus-follows-mouse' to t to make it work.

martin