Bug 143173 No error for recursive including when exporting a report to a library
Steps to reproduce: 1.New a library named "Lib", add a lable in it 2.New a report, extends Lib.label 3.Export the report, choose target library "Lib" Expected result: Error to warn the recursive including Actual result: The target library includes itself without error
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/util/ModelUtil.java
{
			String extensionId = (String) source
					.getProperty( IExtendedItemModel.EXTENSION_NAME_PROP );
			destination.getElement( ).setProperty(
					IExtendedItemModel.EXTENSION_NAME_PROP, extensionId );
		}
		else
		{
			assert false;
		}
	}
	/**
	 * Clone the structure list, a list value contains a list of
	 * <code>IStructure</code>.
	 * 
	 * @param list
	 *            The structure list to be cloned.
	 * @return The cloned structure list.
	 */
	private static ArrayList cloneStructList( List list )
	{
		if ( list == null )
			return null;
		ArrayList returnList = new ArrayList( );
		for ( int i = 0; i < list.size( ); i++ )
		{
			Object item = list.get( i );
			if ( item instanceof IStructure )
			{
				returnList.add( ( (IStructure) item ).copy( ) );