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
*             if error encountered when element name is duplicate in the
	 *             target library.
	 * @throws IOException
	 *             if error encountered when writing file.
	 * @throws IllegalArgumentException
	 *             if the element to export is not in design file, or the
	 *             element doesn't has name.
	 */
	public static void exportElement( DesignElementHandle elementToExport,
			String libraryFileName, boolean canOverride )
			throws DesignFileException, SemanticException, IOException
	{
		ElementExporter.checkElementToExport( elementToExport );
		DesignSession session = elementToExport.getModule( ).getSession( );
		LibraryHandle libraryHandle = openOrCreateLibrary( session,
				libraryFileName );
		assert libraryHandle != null;
		exportElement( elementToExport, libraryHandle, canOverride );
		libraryHandle.save( );
		libraryHandle.close( );
	}
	/**
	 * Exports the given element list into one library file. If the library file
	 * is not found, new library file will be created and saved as the given
	 * file name.
	 * 
	 * @param elementsToExport
	 *            list of the element to export, each of which is the instance
	 *            of <code>DesignElementHandle</code>.
	 * @param libraryFileName