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
session = structToExport.getElementHandle( ).getModule( )
						.getSession( );
		}
		
		if ( session == null )
			return;
		LibraryHandle libraryHandle = openOrCreateLibrary( session,
				libraryFileName );
		assert libraryHandle != null;
		
		iter = structsToExport.iterator( );
		while ( iter.hasNext( ) )
		{
			StructureHandle structToExport = (StructureHandle) iter.next( );
			exportStructure( structToExport, libraryHandle, canOverride );
		}
		libraryHandle.save( );
		libraryHandle.close( );
	}
	/**
	 * Exports the given structure into one library. The allowed structures are
	 * <code>EmbeddedImage</code>,<code>CustomColor</code> and
	 * <code>ConfigVariable</code>.
	 * 
	 * @param structToExport
	 *            handle of the structure to export.
	 * @param targetLibraryHandle
	 *            handle of target library
	 * @param canOverride
	 *            indicates whether the structure with the same name in target