[svn-r19395] Purpose: Fixed bug 1903

Description:
    After a C++ API object is closed, its id should be reset regardless
    of the reference count of the underlying HDF5 object.  User reported
    the bug for Group, but it's applicable to all other objects.  Fixed.
Platforms tested:
    Linux/32 2.6 (jam)
    FreeBSD/64 6.3 (liberty)
    SunOS 5.10 (linew)

c++/src/H5DataSet.cpp

@@ -800,10 +800,8 @@ void DataSet::close()
 	{
 	    throw DataSetIException("DataSet::close", "H5Dclose failed");
 	}
-	// reset the id when the dataset that it represents is no longer
-	// referenced
-	if (getCounter() == 0)
-	    id = 0;
+	// reset the id
+	id = 0;
     }
 }