[PATCH] vprintf: Add handler that mutes all output.

[Chris Johns]

> On 23 Mar 2018, at 5:58 pm, Christian Mauderer <christian.mauderer at embedded-brains.de> wrote:
> 
> Hello Chris,
> 
> I added a small note in libbsd.txt. The rest of the patch is left the
> same. If you don't disagree with that, I'll push this slightly adapted
> patch in the next few days.

OK to push. 

Thank you
Chris