Thread: pgsql: Add some documentation about handling of fractions in interval

Log Message:
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Add some documentation about handling of fractions in interval input.
(It's always worked like this, but we never documented it before.)

Modified Files:
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    pgsql/doc/src/sgml:
        datatype.sgml (r1.232 -> r1.233)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datatype.sgml?r1=1.232&r2=1.233)