gnus don't decode rfc2047 encoded `Newsgroups:' line in header

[Zhang Wei]

While posting articles to a group with chinese `Newsgroup' name, the
article Gcc-ed to my sent.news group has a rfc2047 encoded
`Newsgroups:' line, but gnus don't decode it when I read this article.

This is the message Gcc-ed to my sent.news group:

--8<---------------cut here---------------start------------->8---
Newsgroups: =?gb2312?B?yMvOxNLVyvUuzsTRpy65xbT6zsTRpy667MKlw84=?=
Subject: =?gb2312?B?1tjFxLrswqXDztfuusO1xLe9t6jKx8XEs8kzRLavu63GrA==?=
X-Draft-From: ("nntp+news.newsfan.net:ÈËÎÄÒÕÊõ.ÎÄѧ.¹Å´úÎÄѧ.ºìÂ¥ÃÎ" "")
From: Brep <address@hidden>
Date: Sat, 30 Sep 2006 22:24:33 +0800
Message-ID: <address@hidden>
User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/23.0.0 (gnu/linux)
Cancel-Lock: sha1:nsF/A8IPNnlEKJR5bOypF1opA14=
MIME-Version: 1.0
Content-Type: text/plain; charset=gb2312
Content-Transfer-Encoding: base64
Lines: 2
Xref: emacsfans.org sent.news:34

1eLR+bLFxNzL3NTss/bIw7TzvNLC+tLitcSxpqGi9+yhou7O0M7P86GjDQrP1sq1ysC959bQtcTV
5sjLutzE0cL61+PSqsfzoaMNCg0KDQo=
--8<---------------cut here---------------end--------------->8---

I don't know if the server changed the header of my article, but the
message received back from the server is different from that one
Gcc-ed to my sent.news group, the `Newsgroups:' line is not rfc2047
encoded. gnus could correctly decode this message.

this is the message received back from the server:

--8<---------------cut here---------------start------------->8---
Newsgroups: ÈËÎÄÒÕÊõ.ÎÄѧ.¹Å´úÎÄѧ.ºìÂ¥ÃÎ
Subject: =?gb2312?B?1tjFxLrswqXDztfuusO1xLe9t6jKx8XEs8kzRLavu63GrA==?=
From: Brep <address@hidden>
Message-ID: <address@hidden>
User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/23.0.0 (gnu/linux)
Cancel-Lock: sha1:nsF/A8IPNnlEKJR5bOypF1opA14=
MIME-Version: 1.0
Content-Type: text/plain; charset=gb2312
Content-Transfer-Encoding: 8bit
NNTP-Posting-Host: 60.216.185.203
X-Trace: NFNewsServer4.NewsFan.NET 1159626263 60.216.185.203 (30 Sep 2006 
22:24:23 +0800)
Organization: News.NewsFan.NET
Lines: 4
Date: 30 Sep 2006 22:24:23 +0800
Path: NFNewsServer4.NewsFan.NET!not-for-mail
Xref: NFNewsServer4 ÈËÎÄÒÕÊõ.ÎÄѧ.¹Å´úÎÄѧ.ºìÂ¥ÃÎ:2975

ÕâÑù²ÅÄÜËÜÔì³öÈôó¼ÒÂúÒâµÄ±¦¡¢÷ì¡¢îÎÐÎÏó¡£
ÏÖʵÊÀ½çÖеÄÕæÈ˺ÜÄÑÂú×ãÒªÇó¡£
--8<---------------cut here---------------end--------------->8---

My emacs is bulit from the emacs-unicode-2 branch:

GNU Emacs 23.0.0.1 (i686-pc-linux-gnu, GTK+ Version 2.8.18) of 2006-09-27 on 
debian