[Email-SIG] support CJKCodecs in Charset.py

[Jason R. Mastaler]

Should we support CJKCodecs in Charset.py?  See
http://cjkpython.i18n.org/.

Currently we use a combination of 3 separate packages to support
Japanese, Chinese, and Korean.  Switching to cjkcodecs would support
all of them with just one package.

In addition, 2 of the 3 packages we currently support are obsolete.
KoreanCodecs and ChineseCodecs have been revoked in favor of
cjkcodecs, so the code is no longer even available.  JapaneseCodecs is
still available, but has not been developed in over a year.  cjkcodecs
is actively developed, and available in port/package form for a number
of operating systems.

I have a diff against CVS Charset.py that applies support for
cjkcodecs if you are interested.