Bug 213907 Provide a copy constructor for SubqueryDefinition.
Engine need a copy constructor to generate a SubqueryDefinition from an ISubqueryDefinition and change the name of the query.
data/org.eclipse.birt.report.data.adapter/src/org/eclipse/birt/report/data/adapter/impl/DataRequestSessionImpl.java
/*
	 * @see org.eclipse.birt.report.data.adapter.api.DataRequestSession#prepare(org.eclipse.birt.data.engine.api.IQueryDefinition)
	 */
	public IPreparedQuery prepare( IQueryDefinition query )
			throws BirtException
	{
		
		return dataEngine.prepare( query, this.sessionContext.getAppContext( ) );
	}
	/*
	 * @see org.eclipse.birt.report.data.adaptor.impl.IDataRequestSession#closeDataSource(java.lang.String)
	 */
	public void closeDataSource( String dataSourceName ) throws BirtException
	{
		dataEngine.closeDataSource( dataSourceName );
	}
	/*
	 * @see org.eclipse.birt.report.data.adaptor.impl.IDataRequestSession#getModelAdaptor()
	 */
	public IModelAdapter getModelAdaptor( )
	{
		return modelAdaptor;
	}
	/*
	 * @see org.eclipse.birt.report.data.adaptor.impl.IDataRequestSession#shutdown()
	 */
	public void shutdown( )
	{
		this.clearCache( this.dataSetCache );
		dataEngine.shutdown( );