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.data/src/org/eclipse/birt/data/engine/impl/PreparedQuery.java
/**
	 * Prepares one expression
	 * 
	 * @param expr
	 * @param groupLevel
	 * @param cx
	 * @param reg
	 */
	private void prepareExpression( IBaseExpression expr, int groupLevel,
			Context cx, AggregateRegistry reg )
	{
	    ExpressionCompiler compiler = this.expressionCompiler;
	    
	    if ( expr instanceof IScriptExpression )
	    {
	    	String exprText = ((IScriptExpression) expr).getText();
	    	CompiledExpression handle = compiler.compile( exprText, reg, cx);
	    	expr.setHandle( handle );
	    }
	    else if ( expr instanceof IConditionalExpression )
	    {
	    	
	    	
	    	IConditionalExpression ce = (IConditionalExpression) expr;
	    	ce = transformConditionalExpression( ce );
			
	    	prepareExpression( ce.getExpression(), groupLevel, cx, reg );
	    	if ( ce.getOperand1() != null )
		    	prepareExpression( ce.getOperand1(), groupLevel, cx, reg );
	    	if ( ce.getOperand2() != null )