bug#51733: 27.1; Detect impossible email addresses better

[Eli Zaretskii]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: larsi@gnus.org,  51733@debbugs.gnu.org
> Date: Wed, 19 Jan 2022 13:49:20 +0100
> 
> mail-header-parse-address assumes that the display name or the local
> name starts with a (subset of) ASCII.

Is that expectation reasonable?  I can show you many email addresses
that violate that.