npgsql - Npgsql2: Handle negative values (thanks to Mathieu Fenniak

Log Message:
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Handle negative values (thanks to Mathieu Fenniak <mathieu@fenniak.net>) and singular values such as "1 day"

Modified Files:
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Npgsql2/src/NpgsqlTypes:
DateDatatypes.cs (r1.2 -> r1.3)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/npgsql/Npgsql2/src/NpgsqlTypes/DateDatatypes.cs.diff?r1=1.2&amp;r2=1.3)