wxWindows UTF-8 support

Dear Andreas,

wxWindows includes an mbconv class to convert text into/from UTF-8:
http://www.lpthe.jussieu.fr/~zeitlin/wxWindows/docs/wxwin457.htm#unicode
http://www.lpthe.jussieu.fr/~zeitlin/wxWindows/docs/wxwin458.htm#mbconvclasses

It seems that wxWindows supports all encodings. It would allow pgAdmin3 to map
PostgreSQL encoding, without data stream conversion (without set
client_encoding = foo). Example:

- PostgreSQL server : KOI8-R (old russian encoding supported by PostgreSQL)
- Client encoding : KOI8-R
- pgAdmin3 : strings are converted in UTF-8 at display time.

The world is marvelous, don't you think?
Cheers, Jean-Michel