BUG #3453: Error on COPY TO/FROM 'non-ascii-path'

The following bug has been logged online:

Bug reference: 3453
Logged by: ITAGAKI Takahiro
Email address: itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp
PostgreSQL version: 8.2, 8.3dev
Operating system: independent (especially Windows)
Description: Error on COPY TO/FROM 'non-ascii-path'
Details:

When I set postgres a different character encoding from OS, COPY TO/FROM
'non-ascii-path' cannot open the path. The cause of the problem is that we
pass path-strings encoded in the server encoding to open() directly without
respect to the OS's native encodings.

It will be worse in Windows East Asia versions; Postgres doesn't support
their encodings as server encodings, so we cannot use non-ascii filenames
there.