Emacs 22.1.90 can't save chinese-gb2312 file

["Zhang Wei" <id.brep@gmail.com>]

When I save a file in gb2312 coding system, I got the following
compliant, all of the chinese punctuation characters can't be encoded
with gb2312:
------------------------------------------------------------------------------
These default coding systems were tried to encode text
in the buffer `test':
  chinese-iso-8bit
However, each of them encountered characters it couldn't encode:
  chinese-iso-8bit cannot encode these: ， 。 、 ？

Click on a character (or switch to this window by `C-x o'
and select the characters by RET) to jump to the place it appears,
where `C-u C-x =' will give information about it.

Select one of the safe coding systems listed below,
or cancel the writing with C-g and edit the buffer
   to remove or modify the problematic characters,
or specify any other coding system (and risk losing
   the problematic characters).

  utf-8 utf-16 utf-16 utf-16 utf-16be utf-16le iso-2022-7bit
--------------------------------------------------------------------------
C-u C-x = gives:
--------------------------------------------------------------------------
  character: 。 (302786, #o1117302, #x49ec2, U+3002)
    charset: mule-unicode-2500-33ff (Unicode characters of the range
U+2500..U+33FF.)
 code point: #x3D #x42
     syntax: w 	which means: word
buffer code: #x9C #xF2 #xBD #xC2
  file code: not encodable by coding system chinese-iso-8bit
    display: by this font (glyph code)
     -outline-Courier
New-normal-r-normal-normal-13-97-96-96-c-*-iso10646-1 (#x3002)

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