pgsql: Add missing entry for PG_WIN1250 encoding, per gripe from Pavel

Log Message:
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Add missing entry for PG_WIN1250 encoding, per gripe from Pavel Stehule.
Also enable translation of PG_WIN874, which certainly seems to have an
obvious translation now, though maybe it did not at the time this table's
ancestor was created.

Modified Files:
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    pgsql/src/port:
        chklocale.c (r1.5 -> r1.6)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/port/chklocale.c?r1=1.5&r2=1.6)