bug#742: tool-bar and diary on XP

[Jason Rumney]

> M-x calendar 
> (in calendar window) right mouse click
> select Show diary
>
> RESULT: diary is shown, but tool bar is disabled.
>         Tool bar is not reenabled until another file
>         is visited.
>   

I have fixed this in the Emacs 22 branch by resetting the mouse button 
state when coming out of the popup menu, as we don't get the up event in 
the Emacs window for the corresponding down event that caused the menu 
to be displayed.