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

[Ansgar <ansgar@debian.org>]

Package: debian-policy

5.6.2 Maintainer currently states:

+---
| The package maintainer’s name and email address. The name must come
| first, then the email address inside angle brackets <> (in RFC822
| format).
|
| If the maintainer’s name contains a full stop then the whole field
| will not work directly as an email address due to a misfeature in the
| syntax specified in RFC822
+---

There is an updated version (RFC 5322) that should be used instead. 
Notably RFC 5322 is more restrictive on the local part (whitespace and
escape sequences are no longer allowed except as obsolete syntax).

Furthermore RFC 6532 extends RFC 5322 and allows non-ascii-UTF-8 in
local parts (and other places).  That should probably be allowed as
well.

So, Policy should probably:
 - Refer to RFC 5322.
 - Forbid the obsolete syntax (RFC 5322, Section 4 "Obsolete Syntax").
 - Allow the extensions from RFC 6532.

Ansgar