BUG #5780: Case insensitive regular expressions

The following bug has been logged online:

Bug reference:      5780
Logged by:          Thomas Bakketun
Email address:      thomasb@copyleft.no
PostgreSQL version: 8.4.5
Operating system:   Ubuntu 10.04.1 LTS
Description:        Case insensitive regular expressions
Details:

Apparently case insensitivity in regular expressions only works for ASCII
characters.

ksys@nallemaja:~$ psql -l
                                  List of databases
   Name    |  Owner   | Encoding |  Collation  |    Ctype    |   Access
privileges
-----------+----------+----------+-------------+-------------+--------------
---------
 ksys      | ksys     | UTF8     | nb_NO.UTF-8 | nb_NO.UTF-8 |
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
 s2ksys    | ksys     | UTF8     | nb_NO.UTF-8 | nb_NO.UTF-8 |
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres
                                                             :
postgres=CTc/postgres
 template1 | postgres | UTF8     | nb_NO.UTF-8 | nb_NO.UTF-8 |
 template2 | postgres | UTF8     | nb_NO.UTF-8 | nb_NO.UTF-8 |
 test1     | ksys     | UTF8     | nb_NO.UTF-8 | nb_NO.UTF-8 |
(7 rows)

ksys@nallemaja:~$ psql ksys
psql (8.4.5)
Type "help" for help.

ksys=> select 'Øst' ilike 'øst', 'Øst' ~* 'øst';
 ?column? | ?column?
----------+----------
 t        | f
(1 row)

The different behavior of ilike and case insensitive regular expressions is
surprising. I would have expected both to return true. The documentation
makes it clear ilike depends on the current locale, but not so regarding
regular expressions.