Обсуждение: pgsql: Fix varlena.c routines to allow 1-byte-header text values.

Log Message:
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Fix varlena.c routines to allow 1-byte-header text values.  This is now
demonstrably necessary for text_substring() since regexp_split functions
may pass it such a value; and we might as well convert the whole file
at once.  Per buildfarm results (though I wonder why most machines aren't
showing a failure).

Modified Files:
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    pgsql/src/backend/utils/adt:
        varlena.c (r1.157 -> r1.158)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/varlena.c?r1=1.157&r2=1.158)