pgsql: Suppress time zone name (%Z) when logging timestamps in xlog.c

Log Message:
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Suppress time zone name (%Z) when logging timestamps in xlog.c startup
on Windows.  This is yet another manifestation of the problem that Windows
returns time zone names that may be in a different encoding than we are using.
I've put a better solution in HEAD, but the back branches need a simple patch.
Per report from Hiroshi Saito.

Tags:
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REL8_2_STABLE

Modified Files:
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    pgsql/src/backend/access/transam:
        xlog.c (r1.258 -> r1.258.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xlog.c.diff?r1=1.258&r2=1.258.2.1)