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
{
	/**
	 * Exports the given element 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 elementToExport
	 *            handle of the element to export.
	 * @param libraryFileName
	 *            file name of the target library
	 * @param canOverride
	 *            indicates whether the element 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