wrong -O arg to w3m-m17n

[=?utf-8?B?4KSV4KSq4KS/4KSy?= <klchxbec@xxxxxxxxxxxxxxxxxx>]

Hi,
I'm trying to use emacs-w3m-1.3.6 with w3m-m17n-0.4.1 on
emacs-21.3 to view utf-8 encoded devanagari (hindi) pages
like in http://www.bbc.co.uk/hindi/

This resulted in emacs-w3m displaying ? for utf characters. I
have traced down the problem to emacs-w3m invoking w3m-m17n
using:
-halfdump -o ext_halfdump=1 -o strict_iso2022=0 -I utf-8 -O ISO-2022-JP-2 -T text/html -t 8 -cols 79

If I hardcode emacs-w3m to pass -O UTF-8, and set
w3m-output-encoding-system to 'utf-8, then all utf chars are
displayed properly.

I think something is wrong in how the defcustom in w3m.el
select these encodings since the variable w3m-use-mule-ucs is
found to be nil.

Can someone fix emacs-w3m to detect the presence of utf on
emacs-21.3? I also saw that there is no 'un-define on
emacs-21.3.