Subject: 26.0.90; doc of `picture-open-line'

From: Drew Adams <[email-masked]>
Date: Tue, 2 Jan 2018 09:19:31 -0800 (PST)

The doc string makes it sound like the ARG is optional.
And it doesn't speak of prefix arg (it should).

It should just say that it inserts the numeric prefix arg number of
lines.

In GNU Emacs 26.0.90 (build 3, x86_64-w64-mingw32)
 of 2017-10-13 built on LAPHROAIG
Repository revision: 906224eba147bdfc0514090064e8e8f53160f1d4
Windowing system distributor 'Microsoft Corp.', version 6.1.7601