* OdbcCommandTest.cs: Added test for bug #341743.

* OdbcCommandTest.cs: Added test for bug #341743.
* OdbcColumn.cs: Treat OdbcType.Numeric as decimal.
* OdbcConnection.cs: Keep (weak) list of commands to allow us to
dispose them (and free their corresponding statement handles) when
the connection is closed. Fixed bug #341743.
* OdbcCommand.cs: Add internal Unlink method that is invoked when the
OdbcConnection is disposed, and which frees the statement handle.
Modified ExecuteNonQuery helper to take CommandBehavior and rename
freeHandle argument to createReader. Added CommandBehavior argument
to ExecSQL. Added FreeStatement overload that takes an option to not
perform an unlink. Fixes bug #3417434.

svn path=/trunk/mcs/; revision=122226