npgsql - Npgsql2: Improvements in System.Transactions support.

Log Message:
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Improvements in System.Transactions support. Fixed NullReferenceException initially supported by Chris Coleman.

Modified Files:
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Npgsql2/src/Npgsql:
NpgsqlPromotableSinglePhaseNotification.cs (r1.5 -> r1.6)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/npgsql/Npgsql2/src/Npgsql/NpgsqlPromotableSinglePhaseNotification.cs.diff?r1=1.5&r2=1.6)
NpgsqlResourceManager.cs (r1.3 -> r1.4)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/npgsql/Npgsql2/src/Npgsql/NpgsqlResourceManager.cs.diff?r1=1.3&r2=1.4)
NpgsqlTransactionCallbacks.cs (r1.4 -> r1.5)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/npgsql/Npgsql2/src/Npgsql/NpgsqlTransactionCallbacks.cs.diff?r1=1.4&r2=1.5)