some encodings aren't supported

Hi

And, some encodings aren't supported by PostgreSQL yet:
BIG5, GB18030, GBK, JOHAB, SJIS, SHIFT_JIS_2004, UHC
See here: http://www.postgresql.org/docs/8.4/static/multibyte.html
But all of them can be selected in new Database dialog.

I checked some PostgreSQL sources.
some functions are defined in: backend/utils/mb/encnames.c
pg_valid_server_encoding_id can check
whether an enconding is supported by server.
It invoke macro PG_VALID_BE_ENCODING.
And it is included in libpq-fe.h

Patches are attached.
I didn't define pg_encoding_to_char function in pgConn class.
dlgDatabase is still invoke connection->ExecuteScalar(
wxT("SELECT pg_encoding_to_char(") + NumToStr(encNo) + wxT(")"));

-----------------------------------------------
Quan Zongliang
quanzongliang(at)gmail(dot)com