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/util/ModelUtil.java
int count = element.getDefn( ).getSlotCount( );
		for ( int i = 0; i < count; i++ )
		{
			Iterator iter = element.getSlot( i ).iterator( );
			while ( iter.hasNext( ) )
			{
				DesignElement e = (DesignElement) iter.next( );
				IElementDefn targetDefn = e.getDefn( );
				if ( defn.isKindOf( targetDefn ) )
					return true;
				if ( containElement( e, defn ) )
					return true;
			}
		}
		return false;
	}
	/**
	 * Determines whether there is a child in the given element, which is kind
	 * of the given element definition.
	 * 
	 * @param element
	 *            the element to find
	 * @param elementName
	 *            the element definition type
	 * @return true if there is a child in the element whose type is the given
	 *         definition, otherwise false
	 */
	public static boolean containElement( DesignElement element,
			String elementName )