Apply pending vertical space (pvs) before HTML .li blocks

Problem reported in team discussion by tfkowal: http://www.pgdp.net/phpBB2/viewtopic.php?p=999955#999955

This fix applies any current pvs via a standalone <div> prior to handling an HTML .li block.

(Note that Nigel came up with a solution for Tom that does not require the .li block, but it seems reasonable to me that the pvs should apply before the .li block rather than after it.)