npgsql - Npgsql2: Added fix to return CLR type when working with

Log Message:
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Added fix to return CLR type when working with NpgsqlInet and IPAddress types in NpgsqlDataReader.GetValue(). See http://pgfoundry.org/forum/message.php?msg_id=1006360 for more info about that.
Also, changed implicit operator to explicit operator because it throws exceptiomn. Documentation says implicit operators shouldn't throw exceptions.

Modified Files:
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Npgsql2/src/NpgsqlTypes:
NpgsqlTypes.cs (r1.13 -> r1.14)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/npgsql/Npgsql2/src/NpgsqlTypes/NpgsqlTypes.cs?r1=1.13&r2=1.14)
NpgsqlTypesHelper.cs (r1.36 -> r1.37)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/npgsql/Npgsql2/src/NpgsqlTypes/NpgsqlTypesHelper.cs?r1=1.36&r2=1.37)