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
*            library will be overriden.
	 * 
	 * @throws SemanticException
	 *             if error encountered when adding new structure to library or
	 *             value setting.
	 */
	public static void exportStructure( StructureHandle structToExport,
			LibraryHandle targetLibraryHandle, boolean canOverride )
			throws SemanticException
	{
		ElementExporter.checkStructureToExport( structToExport );
		ElementExporter exporter = new ElementExporter( targetLibraryHandle );
		exporter.exportStructure( structToExport, canOverride );
	}
	/**
	 * Export the report design to a library file specified by the file name. If
	 * the library file is not found, new library file will be created and saved
	 * as the given name.
	 * 
	 * @param designToExport
	 *            the design which need to be exported
	 * @param libraryFileName
	 *            target library file name
	 * @param canOverride
	 *            indicates whether the element with the same name in target
	 *            library will be overriden.
	 * @param genDefaultName
	 *            if true, a default name will be generated if an element
	 *            doesn't has a name. if false, an exception will be throwed
	 *            indicate that the element to export must has a name