bug#31240: 26.1; mouse-save-then-kill does not kill rectangles

[Charles A. Roelli]

> From: Federico Tedin <federicotedin@gmail.com>
> Date: Sun, 19 Aug 2018 23:26:59 -0300
> 
> I've looked into this bug. Its seems like the problem is in mouse.el,
> where line 1610 could be changed from:
> 
> (kill-region (mark t) (point)))
> 
> to:
> 
> (kill-region (mark t) (point) 'region))
> 
> Which would make kill-region use the (potentially rectangular) region
> instead of BEG and END. The problem is, many mouse-related functions
> still use functions such as filter-buffer-substring and delete-region,
> which are not rectangular-region aware. Would submitting a patch for
> this line only make sense?

Thanks for looking into this.  It would be great to squash all these
problems with one patch to get a consistent behavior.  I will retitle
the bug to make that clearer.