[proven WIn32SS!] ListView arrows should not flash upon autoscrolling a listView (happens in many NSIS installers)

0.4.9-RC-35-g3eb03ef down to at least 0.4.0rls is affected (most likely since forever)

When you have a large listview where automatically new text is pushed into (autoscroll to bottom is activated).

You can see that in almost all NSIS installers for example, in this case I used the Orwell DevCPP one from rapps, but as said, you can use almost everyone.

A trivial issue for itself, but eventually it helps us to better understand some of our other scrollbar issues.

Observed behavior
The small-triangle-arrows of the scrollbar do flash erroneously.
0.4.9-RC-35-g3eb03ef__triangles.webm
bootcd-65496-dbg affected as well, very old issue.

Expected behavior
On 2k3 those scrollbar triangles do not flash, they are drawn enabled the whole time.

Nothing gets logged when performing that.