The problem was that the x position of the btlr text had a 159 twips
difference (it was too close to the cell border), since the text portion
height -> baseline offset calculation worked with the descent, not with
the ascent.

The position of the text now matches exactly what Word does.

As a side-effect this means that multiple portions in a line and also
multiple lines in a text frame now work correctly.

Change-Id: Ic139db328e2a913e5cae4026886c3410cdab357d
Reviewed-on: https://gerrit.libreoffice.org/67823
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>