BUG #5903: Turkish encoding problem

The following bug has been logged online:

Bug reference: 5903
Logged by: Sarp Akal
Email address: sarp(at)dms-tech(dot)com
PostgreSQL version: 9.0.2
Operating system: Windows Server 2008 R2 x64
Description: Turkish encoding problem
Details:

The server is setup for UTF8 encoding and collation and character type are
Turkish_Turkey.1254

The following code fails:

select lower('İ') --> Lowercase of turkish capital I-with dot returns
exactly the same character.

select upper('ı') --> Uppercase of turkish small i-without dot returns
exactly the same character.

select lower('I') --> Lowercase of turkish capital I returns i where it
should be i-without dot.

select upper('i') --> Uppercase of turkish small returns I where it should
be I-with dot.