Bugfix for experimental function merge pagenumbers

It's incredible how one can mess up this function...
Bugfix: underline glue after hyphen

When we insert a glue after a hyphen, it should
possibly also be underlined.
Bugfix for table head

When table head + first line does not fit onto
the current page, the table head was put on the page
by itself, continuing with the second table head
plus the first row.
Bugfix for finding a suitable place in an area

Both, the row start + row end should be shifted down.
Safety net for "no data available"