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/PDFBlockStackingLM.java
keepWith = keepWith || keepWithNext || pageBreakAvoid;
		
		if(!keepWith && !keepWithPrevious)
		{
			clearCache( );
		}
		AbstractArea aArea = (AbstractArea)area;
		if(keepWithCache.getHeight( ) + aArea.getAllocatedHeight( ) + getCurrentBP() > getMaxAvaHeight())
		{
			context.setAutoPageBreak( true );
			return false;
		}
		else
		{
			if(keepWithPrevious || keepWith)
			{
				keepWithCache.add( area );
			}
			else
			{
				addToRoot(aArea);
			}
		}
		return true;
	}
	public int getLineHeight( )
	{
		if ( content != null )
		{