TM format can mix encodings in to_char()

Hackers,

I will use as an example the code in the regression test
'collate.linux.utf8'.
There you can find:

SET lc_time TO 'tr_TR';
SELECT to_char(date '2010-04-01', 'DD TMMON YYYY');
to_char
-------------
01 NIS 2010
(1 row)

The problem is that the locale 'tr_TR' uses the encoding ISO-8859-9
(LATIN5),
while the test runs in UTF8. So the following code will raise an error:

SET lc_time TO 'tr_TR';
SELECT to_char(date '2010-02-01', 'DD TMMON YYYY');
ERROR: invalid byte sequence for encoding "UTF8": 0xde 0x75

The problem seems to be in the code touched in the attached patch.

Regards,

Juan Jose Santamaria Flecha