bug#27530: patch to cut and copy secondary

[Drew Adams]

> >> The function exchanges point and mark.
> >> When there is region, this also creates secondary.
> >
> > Why?  What if I want to just exchange point and mark,
> > and not also copy the region to the secondary?
> 
> I proposed to put a function in lisp/mouse.el that can be remapped to
> C-x C-x by an user.  I did not propose to replace
> exchange-point-and-mark.
> 
> I create the secondary selection every wheel scroll as memory of
> region.  To me, C-x C-x works well to recall region.

I see.  I misunderstood.  I thought that you were proposing
to bind keys/mouse by default.  Adding useful commands can't
hurt.