bug#37700: 27.0.50; undo mouse-drag-and-drop-region ineffective

[martin rudalics]

> On revision of writing, I often want to move a sentence around to fit
> into right place, without loosing the sentence from sight.  Most of the
> time I cannot relocate the sentence to the best place by single
> drag-and-drop operation thus I want to maintain region active.
>
> I found that I did not notice problem pointed by Mattias because I
> assign `undo' by `redo+.el' to C-/.  I agree that undo behavior by C-/
> with Emacs -Q is inconvenient!

I think that we should provide an option to not enable the region
after dropping and maybe even make it the default.

martin