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 IllegalArgumentException
	 *             if the element to export is not in design file.
	 */
	public static void exportElement( DesignElementHandle elementToExport,
			LibraryHandle targetLibraryHandle, boolean canOverride )
			throws SemanticException
	{
		ElementExporter.checkElementToExport( elementToExport );
		ElementExporter exporter = new ElementExporter( targetLibraryHandle );
		exporter.exportElement( elementToExport, canOverride );
	}
	/**
	 * Exports the given structure into one library. The allowed structures are
	 * <code>EmbeddedImage</code>,<code>CustomColor</code> and
	 * <code>ConfigVariable</code>. If the library file is not found, new
	 * library file will be created and saved as the given file name.
	 * 
	 * @param structToExport
	 *            handle of the structure to export.
	 * @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.