bug#3717: M-x man completion

[Kevin Ryde]

Juri Linkov <juri@jurta.org> writes:
>
> The only problem I see is with the "2 chmod" format completion.

It's quite important too, as it's the natural format from the man
command line.

> because manual names that begin with a digit are very rare.
> Here I can find only one such command - "7z".

Debian has an "822-date" program too, I don't know of any others.
With some care it should be possible to treat them like any other name.