Bug 178519 Problems in multi-rows header
Please see the attachments.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/layout/pdf/PDFTableLM.java
* 1. resolve all unresolved cell 2. resolve table bottom border 3.
		 * update height of Root area 4. update the status of TableAreaLayout
		 */
		int borderHeight = 0;
		if ( layout != null )
		{
			layout.resolveAll( );
			borderHeight = layout.resolveBottomBorder( );
			layout.remove( (TableArea) root );
		}
		
		root.setHeight( getCurrentBP( ) + getOffsetY( ) + borderHeight );
	}
	public int getColumnNumber( )
	{
		return columnNumber;
	}
	/**
	 * resolve cell border conflict
	 * 
	 * @param cellArea
	 */
	public void resolveBorderConflict( CellArea cellArea )
	{
		if ( layout != null )
		{
			layout.resolveBorderConflict( cellArea );
		}
	}
	private class ColumnWidthResolver