bug#22107: this-command-keys no longer returns prefix argument

[Eli Zaretskii]

> From: Kaushal Modi <kaushal.modi@gmail.com>
> Date: Wed, 11 May 2016 13:33:18 +0000
> 
> I looked at the related commit based on this bug:
> http://git.savannah.gnu.org/cgit/emacs.git/commit/src/keyboard.c?h=emacs-25&id=9d2b8e768f2015a89f7609dedf7b28ea5e8123b5
> 
> 
> It's commit log says "Restore the feature whereby C-u was part of 
> this-command-keys, but not of
> this-single-command-keys.". But it looks like no restore happened. "^U" is 
> still not part of this-command-keys.

Because that commit was reverted, see commit 0b7d6b0.

AFAIR, Stefan thought that the current behavior is the correct one.