[Bug: 21.5-b28] dired decode setting get confused after gnus run

[Aidan Kehoe]

 Ar an seachtú lá de mí Bealtaine, scríobh It's me FKtPp ;): 

 > ================================================================
 > Dear Bug Team!
 > 
 > I find that dired buffer decode setting will get confused whenever I
 > finished reading news with gnus.
 > 
 > Step to reproduce this bug:
 > 
 > 1. open a dired buffer on directory contains some file with Chinese in
 > their filename.
 >  => Chinese characters get properly displayed (chinese-gb2312) in the dired buffer
 > 
 > 2. kill the buffer, and run gnus by running `M-x gnus <RET>'
 > 3. quit gnus by typing `q'
 > 4. re-open dired on the same direcotry (with those chinese-files)
 >  => Chinese characters get garbled (displayed in latin-iso8859-1)
 > 
 > Maybe you can also reproduce this by using some file with
 > japanese/korean characters in their filename.
 > 
 > ================================================================
 > 
 > [...]
 > 
 > Coding system aliases:
 > 
 >   'native                              is aliased to utf-8
 >   'file-name                           is aliased to binary
 >   'mswindows-multibyte-system-default  is not a coding system alias

file-name should be an alias of utf-8, not of binary. Looks like Gnus is
trashing it, or the related variable file-name-coding-system, but a quick
grep doesn't point me to where--it's always bound, not set. 

Can you do a M-x gnus-bug RET, and CC xemacs-beta? The version info there
would seem to be relevant. 

-- 
¿Dónde estará ahora mi sobrino Yoghurtu Nghé, que tuvo que huir
precipitadamente de la aldea por culpa de la escasez de rinocerontes?