[kaffe] Japanese charsets support

[Ito Kazumitsu]

Hi,

Formerly, when Kaffe had original ByteToChar and CharToByte converters,
we could use such Japanese charsets or charset aliases as EUC_JP,
Shift_JIS, and MS932.

Now that kaffe uses gnu.java.nio.charset.iconv package, those charsets
cannot be used any more.

EUC_JP:    missing in the aliases list of EUC-JP.

Shift_JIS: iconv's behavior may be correct in the light of the standard,
           but in the real life, we need something slightly deifferent.
           See http://savannah.gnu.org/bugs/?func=detailitem&item_id=13111

MS932 or officially Windows-31J:
           iconv does not support this. iconv does support CP932,
           which is similar to MS932, but iconv's CP932 is slightly
           different from MS932.

As a solution of this issue, I have made my own CharsetProvider as
a wrapper of gnu.java.nio.charset.iconv.IconvProvider and put it at
http://www.jsdi.or.jp/~maczuka/kaffe/IconvJapaneseCharsetProvider.java

I would like to contibute this to Kaffe.  Where in the source tree
should I put it ?