bug#26845: gnutls-verify-error doc-string

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Date: Mon, 08 May 2017 16:34:17 -0400
> 
> I'm going to be that guy and say that the doc-string of
> gnutls-verify-error is so terse that it isn't useful.
> 
> "If non-nil, this should be a list of checks per hostname regex or t."
> 
> This is the whole thing. It's a defcustom, but I don't see how anyone
> can set it based on that information.
> 
> What does it mean if it is nil?
> What does it mean if it is t?
> What format does the "list of checks per hostname" take?

Thanks, fixed.