npgsql - Npgsql2: Fixed mapping for char parameter values.

Log Message:
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Fixed mapping for char parameter values. Now, Npgsql won't throw a DbType cast exception when trying to assign a char to a parameter value. Also, Npgsql will send the proper cast ::char when sending queries. See http://pgfoundry.org/forum/message.php?msg_id=1003367 for discussion about that. Thanks Andrus Moor for testcase.

Modified Files:
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Npgsql2/src/NpgsqlTypes:
NpgsqlTypesHelper.cs (r1.14 -> r1.15)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/npgsql/Npgsql2/src/NpgsqlTypes/NpgsqlTypesHelper.cs.diff?r1=1.14&r2=1.15)
Npgsql2/testsuite/noninteractive/NUnit20:
CommandTests.cs (r1.9 -> r1.10)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/npgsql/Npgsql2/testsuite/noninteractive/NUnit20/CommandTests.cs.diff?r1=1.9&r2=1.10)