Do not skip data after horizontal lines in the layout.

Do not skip data after horizontal lines in the layout.
Instead, let one line of input data add two new spans
to the tbl tree during one single call of tbl_data().
Note that this causes the horizontal line to get parsed
into the tbl tree, but not yet used in the output,
which will be fixed next.
Avoids data loss in cpu(4/hppa).
ok kristaps@