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/api/util/ElementExportUtil.java
*            of <code>StructureHandle</code>.
	 * @param libraryFileName
	 *            file name of the target library
	 * @param canOverride
	 *            indicates whether the structure with the same name in target
	 *            library will be overriden.
	 * 
	 * @throws DesignFileException
	 *             if error encountered when open library file with the given
	 *             file name.
	 * @throws SemanticException
	 *             if error encountered when adding new structure to library or
	 *             value setting.
	 * @throws IOException
	 *             if error encountered when writing file.
	 * @throws IllegalArgumentException
	 *             if the element to export is not in design file.
	 */
	public static void exportStructures( List structsToExport,
			String libraryFileName, boolean canOverride )
			throws DesignFileException, SemanticException, IOException
	{
		DesignSession session = null;
		
		Iterator iter = structsToExport.iterator( );
		while ( iter.hasNext( ) )
		{
			StructureHandle structToExport = (StructureHandle) iter.next( );
			ElementExporter.checkStructureToExport( structToExport );
			if ( session == null )