BUG #12754: The 'OF' template pattern of to_char() print incorrect results with negative offsets with minutes

The following bug has been logged on the website:

Bug reference:      12754
Logged by:          David Pozsar
Email address:      david.pozsar@gmail.com
PostgreSQL version: 9.4.0
Operating system:   Windows 7
Description:

If the current time-zone has minutes and is negative, to_char('OF') prints a
negative sign before the minute part too.

Code, to reproduce:

set time zone interval '-02:30';
-- or: set timezone to -2.5;
select ts::text, to_char(ts, 'YYYY-MM-DD HH24:MI:SSOF')
from (values (timestamptz '2015-02-10 07:05:15+00')) v(ts);

Output:

            ts             |          to_char
---------------------------+----------------------------
 2015-02-10 04:35:15-02:30 | 2015-02-10 04:35:15-02:-30

Expected output:

            ts             |         to_char
---------------------------+---------------------------
 2015-02-10 04:35:15-02:30 | 2015-02-10 04:35:15-02:30