Bug#962277: debian-policy: Maintainer address: move away from RFC822 to RFC5322 + RFC6532

[Ansgar <ansgar@debian.org>]

On Fri, 2020-06-05 at 15:23 +0200, Ansgar wrote:
> So, Policy should probably:
>  - Refer to RFC 5322.
>  - Forbid the obsolete syntax (RFC 5322, Section 4 "Obsolete Syntax").
>  - Allow the extensions from RFC 6532.

Maybe Policy should also refer to either `mailbox` or `name-addr` for
the Maintainer field (`name-addr` requires angle brackets `<>`) and
either `mailbox-list`, `address-list`, or even `group-list` (would also
allow groups) for Uploaders.

`mailbox` allows plain address (without angle brackets `<>`); the
display-name is optional in `name-addr` as well, so that might be a
small change, but one could require it to be non-empty.

That is a small change for Uploaders as it would allow bare addresses. 
Currently Uploaders would be something like

  name-addr-list = name-addr *("," name-addr)

which doesn't exist in RFC 5322.

Personally I would probably just make Maintainer a `name-addr` and
Uploaders either `mailbox-list` (most restrictive) or `group-list`
(most permissive).  Debian-specific constructs should probably be
avoided.

Ansgar