Automatic code conversion between UNICODE and other encodings

Hi,

I have committed the first implementation of an automatic code
conversion between UNICODE and other encodings. Currently
ISO8859-[1-5] and EUC_JP are supported. Supports for other encodings
coming soon. Testings of ISO8859 are welcome, since I have almost no
knowledge about European languages and have no idea how to test with
them.

How to use:

1. configure and install PostgreSQL with --enable-multibyte option

2. create database with UNICODE encoding
$ createdb -E UNICODE unicode

3. create a table and fill it with UNICODE (UTF-8) data. You could
create a table with even each column having different language.
create table t1(latin1 text, latin2 text);

4. set your terminal setting to (for example) ISO8859-2 or whatever

5. start psql

6. set client encoding to ISO8859-2
\encoding LATIN2

7. extract ISO8859-2 data from the UNICODE encoded table
select latin2 from t1;

P.S. I have used bsearch() to search code spaces. Is bsearch() is
portable enough?
--
Tatsuo Ishii