bug#52086: 27.2; `C-w' should kill active rectangular region (aka rectangle)

[Drew Adams <drew.adams@oracle.com>]

If use C-x SPC, to activate the rectangular region, commands that act on
that active region should, I think, generally act on the selected text,
that is, the text in the rectangle.

`C-w' doesn't do that.  Instead, it kills the text in the region between
point and mark - all of it, including text that is not selected (not
part of the active, rectangular region.

(Yes, there is also `C-x r k', but that acts on a rectangle regardless
of whether the region is active.  It's another way to kill a rectangle.)

I'd call this a bug.  You might see it as an enhancement request.  To
me, it's what users expect, and it's the only behavior consistent with
what users see and the notion of active rectangular region.  `C-w'
should be no different from, say, the replacement commands, when the
region is "noncontiguous".

And we should look out for other possible, similar holdovers: commands
that act on the active region, but don't respect rectangular bounds.

In GNU Emacs 27.2 (build 1, x86_64-w64-mingw32)
 of 2021-03-26 built on CIRROCUMULUS
Repository revision: deef5efafb70f4b171265b896505b92b6eef24e6
Repository branch: HEAD
Windowing system distributor 'Microsoft Corp.', version 10.0.19042
System Description: Microsoft Windows 10 Pro (v10.0.2009.19042.1288)