bug#23707: 25.0.94; Regression in mouse-set-region

[martin rudalics]

> When using the mouse to set a region outside of the current window, the
> region is now created improperly. There are two basic cases:
>
> a) dragging the mouse and ending on or outside the Emacs frame causes no
> region to be created
>
> Steps to reproduce:
>
> 1. emacs -Q
> 2. In the scratch buffer with <mouse-1>, drag the region and end off in
> the menu-bar area.
> 3. The region is not created.
>
> b) dragging the mouse and ending in another Emacs window causes a region
> to be created between the starting point and the point corresponding to
> the ending point *in the other buffer*.
>
> 1. emacs -Q
> 2. C-x 2
> 3. C-x 0
> 4. In the bottom scratch window, drag with your mouse and end somewhere
> in the scratch message int he top window
> 5. The region is created, but ends prematurely at whatever point you
> ended at in the top window.
>
>
> Emacs 24.5 had the correct behaviour of creating a region between the
> starting point and one of the ends of the buffer when dragging outside
> of the current window.
>
> In GNU Emacs 25.0.94.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.18.9)
>   of 2016-05-17 built on lylat
> Windowing system distributor 'Fedora Project', version 11.0.11803000
> Configured using:
>   'configure --with-gif=no'

Both scenarios are easily reproducible on Windows.  Would the attached
patch fix it for you?

Thanks, martin

mouse.diff
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