Make Message more RFC compliant

[Lars Ingebrigtsen <larsi@gnus.org>]

There are recentish (I mean, only a few years old) RFCs that now specify
that From addresses on the form

  From: larsi@gnus.org (Lars Ingebrigtsen)

SHOULD not be generated, because they create problems for some
recipients (*cough* Microsoft Mail *cough*):

Only this form is allowed now:

  From: Lars Ingebrigtsen <larsi@gnus.org>

Michael Stapelberg <stapelberg@debian.org> writes:

>>    Note: Some legacy implementations used the simple form where the
>>    addr-spec appears without the angle brackets, but included the name
>>    of the recipient in parentheses as a comment following the addr-spec.
>>    Since the meaning of the information in a comment is unspecified,
>>    implementations SHOULD use the full name-addr form of the mailbox,
>>    instead of the legacy form, to specify the display name associated
>>    with a mailbox.

So:

The RFC says SHOULD, so Message shouldn't have an easy way to generate
From headers that deviate from the `angles' style.

So I propose to remove the code that reacts to `message-from-style'
(i.e., always generate `angles' From headers), and mark
`message-from-style' as obsolete and note in the doc string that it's no
longer used.

Any objections?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no